Short answer
WhatsApp, LINE, iMessage, and FaceTime can be used over Wi-Fi or cellular data, and a new SIM does not by itself replace the WhatsApp number. LINE keeps showing its registered number until you verify a new one by text or call, WhatsApp requires the new number to receive a text or a call, and Apple says the phone number for iMessage and FaceTime has to be on an active SIM, or you use an email address instead.
Whether a Wakamo Japan plan lists a phone number, and whether WhatsApp, LINE, FaceTime, and iMessage keep a number you already have, is covered in Do I get a Japanese phone number with a Japan eSIM?.
Fact table
As of 2026-10-21
Each claim names its source. The full source list, with the date each page was read, is below.
| Claim | Source |
|---|---|
| WhatsApp's iPhone tab says it does not charge for sending messages and media, or for making voice and video calls. Using WhatsApp requires an internet connection through either a mobile data network or Wi-Fi, and data charges may apply. WhatsApp says to contact your mobile provider about those charges. Data charges might also apply if you use the phone's own messaging or calling system, and WhatsApp gives SMS or MMS to someone who does not have WhatsApp as an example. Both people need WhatsApp installed to send and receive messages and media over WhatsApp. | WhatsApp Help, charges on iPhone |
| WhatsApp's Android tab says it does not charge for messages, media, or voice and video calls. An internet connection through mobile data or Wi-Fi is required, and data charges may apply. SMS or MMS to someone who does not have WhatsApp is the phone's own messaging system. | WhatsApp Help, charges on Android |
| WhatsApp's iPhone article says that if you want to change your phone number or use a new SIM card, you must use the change number feature to transfer the account to the new number. Before that change, the new number must be able to receive SMS texts or phone calls, the new number must have an active cellular connection, and the old number must currently be registered on WhatsApp. The registered number is in WhatsApp settings or your profile. The change is done on the primary phone. WhatsApp says you cannot change the number on WhatsApp Desktop or WhatsApp Web. On the same phone, WhatsApp says to insert the SIM card with the new phone number first. | WhatsApp Help, change number on iPhone |
| WhatsApp's iPhone article says numbers that cannot be registered include VoIP, toll-free numbers, paid premium numbers, universal access numbers, personal numbers, and landlines. Landlines are only accepted on the WhatsApp Business app. | WhatsApp Help, change number on iPhone |
| WhatsApp's Android article says that if you want to change your phone number or use a new SIM card, you must use the change number feature to transfer the account. Before that change, the new number must be able to receive SMS texts or phone calls, and the old number must currently be registered. That Android before-list does not say the new number must have an active cellular connection. The change is done on the primary phone, not on WhatsApp Desktop or WhatsApp Web. On the same phone, WhatsApp says to insert the SIM card with the new phone number first. | WhatsApp Help, change number on Android |
| WhatsApp's Android article says numbers that cannot be registered include VoIP, toll-free numbers, paid premium numbers, universal access numbers, personal numbers, and landlines. Landlines are only accepted on the WhatsApp Business app. | WhatsApp Help, change number on Android |
| WhatsApp says changing the phone number transfers the account information to the new number, including the profile photo, username, display name, privacy settings, WhatsApp contacts, individual chats, and group chats, and deletes the WhatsApp account on the old number so contacts no longer see that old number. WhatsApp says there is no way to revert a change made by mistake. Cloud backups of the chat history are linked to the phone number used when the backup was created, so backups made on the old number can no longer be used to restore the data. WhatsApp says to create a new backup after the change. | WhatsApp Help, about changing phone numbers |
| LINE says the basic features are free to use, whether you use the app domestically or abroad, and that you incur data fees when using LINE. LINE says to check the plan rates and contract of your mobile service provider for those fees. If you use the device outside the country you are contracted in, LINE says international data usage fees may differ, and to refer to that contract or contact the provider. | LINE Help, using LINE for free |
| LINE says that if you cannot send or receive messages, the cause may be the network connection. LINE tells you to turn the 4G, 5G, or Wi-Fi connection off and on, and to switch between a 4G or 5G network and Wi-Fi. | LINE Help, cannot send or receive messages |
| LINE says you can check the phone number registered to the account from Account settings on the main device. LINE says you can only change that phone number if you are using LINE in Hong Kong, Japan, Korea, Taiwan, or Thailand, and that the change verifies the new number by text message or by phone call. LINE says one mobile phone number can verify only one LINE account. Registering a number already registered to another LINE account may make the original account inaccessible. LINE says you cannot change the phone number for 24 hours after transferring the LINE account. | LINE Help, checking or changing your phone number |
| Apple says iMessage messages can be sent to another iPhone or another Apple device over Wi-Fi or cellular-data networks, and that they appear in blue bubbles. If Wi-Fi is unavailable, Apple says those messages are sent over cellular data, and cellular data rates might apply. Apple says RCS needs iOS 18 and a text-messaging plan from a carrier that supports RCS on iPhone, and SMS and MMS need a text-messaging plan that supports them. RCS and SMS/MMS appear in green bubbles, and Apple says both are carrier-provided services. Apple says to contact the carrier. That page does not say which connection carries a green RCS, SMS, or MMS message. | Apple Support, iMessage, RCS, and SMS |
| Apple says you can send iMessage texts over Wi-Fi or cellular service, and that those texts do not count against the SMS, MMS, or RCS allowances in the cellular messaging plan, though cellular data rates may apply. A blue send button means iMessage. A green send button means SMS, MMS, or RCS. | Apple Support, iMessage overview |
| Apple says that to sign in to iMessage or FaceTime you need a cellular data or Wi-Fi connection. On an iPhone, Apple says you need SMS messaging to activate the phone number with iMessage and FaceTime, and that the carrier might charge for that SMS. Apple says you can use an email address instead, chosen under Send & Receive for Messages and under You Can Be Reached By FaceTime At for FaceTime. If the phone number still has no check after 24 hours, Apple says to contact the carrier to make sure you can send and receive international SMS. Apple says FaceTime isn't available in all countries or regions. | Apple Support, activate iMessage or FaceTime |
| Apple says that if you do not activate iMessage or the eSIM when you set up a new iPhone with iOS 26, iMessage does not activate automatically after you set up an eSIM in Settings later. Messages might then cause a Not Delivered alert, appear as SMS or RCS in green bubbles, or come from the email address instead of a phone number. Apple says to turn iMessage off and back on in that situation. | Apple Support, activate iMessage or FaceTime |
| Apple says that to set up a phone number to use with Messages or FaceTime, you need an active SIM or eSIM associated with that number. On the iPhone, that number and the Apple Account are selected for Messages under Send & Receive, and for FaceTime in the list of where you can be reached. | Apple Support, phone number in Messages or FaceTime |
| Apple says you can use FaceTime over Wi-Fi or over cellular on supported iOS or iPadOS devices, and that data rates may apply. With a cellular data plan, Apple says you can use FaceTime without Wi-Fi on an iPhone 4s or later, on iPad Pro, and on iPad (3rd generation or later). Apple says FaceTime, Group FaceTime, or FaceTime audio may not be available in all countries or regions. | Apple Support, use FaceTime |
FAQ
Do WhatsApp messages work when the travel eSIM is the data connection?
WhatsApp's iPhone and Android tabs say using WhatsApp requires an internet connection through a mobile data network or Wi-Fi. WhatsApp says it does not charge for messages, media, or voice and video calls, and that data charges may apply. WhatsApp says to contact your mobile provider about those charges. Both people need WhatsApp installed. SMS or MMS to someone who does not have WhatsApp is the phone's own messaging system, and data charges might apply to that.
Will installing a Japan eSIM change my WhatsApp number?
Not by itself. WhatsApp's iPhone and Android articles say that if you want to change your phone number or use a new SIM card, you must use the change number feature to transfer the account. The number currently registered is the one in WhatsApp settings or your profile.
What does WhatsApp require before the number can change?
On iPhone, WhatsApp says the new number must be able to receive SMS texts or phone calls, and it must have an active cellular connection. On Android, WhatsApp says the new number must be able to receive SMS texts or phone calls. That Android before-list does not say the new number must have an active cellular connection. Both say the old number must currently be registered, and that the change is done on the primary phone, not on WhatsApp Desktop or WhatsApp Web. On the same phone, both say to insert the SIM card with the new phone number first. Numbers WhatsApp says cannot be registered include VoIP, toll-free numbers, paid premium numbers, universal access numbers, personal numbers, and landlines. Landlines are only accepted on the WhatsApp Business app.
What happens to the old WhatsApp number if I complete that change?
WhatsApp says the change transfers your chats, groups, and account information to the new number, and deletes the WhatsApp account on the old number so contacts no longer see it. WhatsApp says a change made by mistake cannot be reverted. Cloud backups stay linked to the number used when the backup was created, so backups made on the old number can no longer restore the data. WhatsApp says to create a new backup after the change.
Do LINE chats work abroad on a data connection?
LINE says the basic features are free domestically or abroad, and that you incur data fees when using LINE. If the device is outside the country on your mobile contract, LINE says international data usage fees may differ, and to check that contract or contact the provider. If messages will not send or arrive, LINE says the network may be the cause, and it names a 4G, 5G, or Wi-Fi connection.
Will my LINE number change when I add the eSIM?
LINE says the number registered to the account is the one shown in Account settings on the main device. That number changes when you verify a new phone number, by text message or by phone call. LINE says you can only make that change if you are using LINE in Hong Kong, Japan, Korea, Taiwan, or Thailand. One mobile number can verify only one LINE account, and registering a number that already belongs to another account may make that original account inaccessible. LINE says you cannot change the number for 24 hours after transferring the account.
Do iMessage texts use the data connection?
Apple says iMessage can be sent to another Apple device over Wi-Fi or cellular-data networks, including over cellular data when Wi-Fi is unavailable. Cellular data rates might apply. Those texts do not count against SMS, MMS, or RCS allowances. They appear in blue bubbles, and a blue send button means iMessage. A green send button means SMS, MMS, or RCS.
Will a green message use the travel line's data?
Apple says RCS and SMS/MMS are carrier-provided and appear in green bubbles. RCS needs iOS 18 and a text-messaging plan from a carrier that supports RCS. SMS and MMS need a text-messaging plan that supports them. Apple says to contact the carrier. Apple says iMessage, in blue bubbles, is sent over Wi-Fi or cellular data. The same page does not say whether a green RCS, SMS, or MMS message uses the travel line's data connection.
Will iMessage or FaceTime switch to a number on the travel eSIM?
Apple says that to set up a phone number for Messages or FaceTime, you need an active SIM or eSIM associated with that number. You select that number and the Apple Account under Send & Receive for Messages, and in the FaceTime list of where you can be reached. On an iPhone, activating that phone number needs SMS, and the carrier might charge for the SMS. Apple says you can use an email address instead. FaceTime can use Wi-Fi or cellular, and data rates may apply. With a cellular data plan, Apple says FaceTime can be used without Wi-Fi on an iPhone 4s or later, on iPad Pro, and on iPad (3rd generation or later). Apple says FaceTime may not be available in all countries or regions.
What if the iMessage phone number will not activate?
Apple says it might take up to 24 hours for the carrier to verify the phone number, and to contact the carrier about sending and receiving international SMS. You can use an email address with iMessage and FaceTime instead. If you set up a new iPhone with iOS 26 and do not activate iMessage or the eSIM at that setup, Apple says iMessage does not activate automatically when you add an eSIM in Settings later. Messages might then show Not Delivered, appear as SMS or RCS in green bubbles, or come from the email address. Apple says to turn iMessage off and back on in that case.
Sources
WhatsApp Help, charges on iPhonefaq.whatsapp.com
The iPhone tab says WhatsApp does not charge for sending messages and media, or for making voice and video calls. Using WhatsApp requires an internet connection through a mobile data network or Wi-Fi. Data charges may apply, and WhatsApp says to contact your mobile provider. Data charges might also apply when you use the phone's own messaging or calling system, including SMS or MMS to someone who does not have WhatsApp. Both people need WhatsApp installed to send and receive messages and media over WhatsApp.
Accessed 2026-10-21.
WhatsApp Help, charges on Androidfaq.whatsapp.com
The Android tab says WhatsApp does not charge for messages, media, or voice and video calls. An internet connection through mobile data or Wi-Fi is required. Data charges may apply. SMS or MMS to someone without WhatsApp is the phone's own messaging system.
Accessed 2026-10-21.
WhatsApp Help, change number on iPhonefaq.whatsapp.com
If you want to change your phone number or use a new SIM card, you must use the change number feature to transfer the account. On the same phone, insert the SIM card with the new phone number first. Before the change, the new number must be able to receive SMS texts or phone calls, the new number must have an active cellular connection, and the old number must currently be registered on WhatsApp. The registered number is in Settings or your profile. The change is done on the primary phone, not on WhatsApp Desktop or WhatsApp Web. Numbers WhatsApp says cannot be registered include VoIP, toll-free, paid premium, universal access numbers, personal numbers, and landlines. Landlines are only accepted on the WhatsApp Business app.
Accessed 2026-10-21.
WhatsApp Help, change number on Androidfaq.whatsapp.com
If you want to change your phone number or use a new SIM card, you must use the change number feature to transfer the account. On the same phone, insert the SIM card with the new phone number first. Before the change, the new number must be able to receive SMS texts or phone calls, and the old number must currently be registered. That before-list does not say the new number must have an active cellular connection. The change is on the primary phone, not Desktop or Web. The unsupported list names VoIP, toll-free, paid premium, universal access numbers, personal numbers, and landlines, with landlines only on the WhatsApp Business app.
Accessed 2026-10-21.
WhatsApp Help, about changing phone numbersfaq.whatsapp.com
Changing the number transfers account information to the new number, including the profile photo, username, display name, privacy settings, contacts, individual chats, and group chats, and deletes the account on the old number. A change made by mistake cannot be reverted. Cloud backups are linked to the phone number used when the backup was created, so backups made on the old number can no longer restore the data. WhatsApp says to create a new backup after the change.
Accessed 2026-10-21.
LINE Help, using LINE for freehelp.line.me
LINE says the basic features are free domestically or abroad, and that you incur data fees when using LINE. It says to check the mobile provider's plan rates and contract. Outside the country on that contract, international data usage fees may differ, and LINE says to check the contract or contact the provider.
Accessed 2026-10-21.
LINE Help, cannot send or receive messageshelp.line.me
LINE says a failure to send or receive messages may be the network connection. The steps include turning the 4G, 5G, or Wi-Fi connection off and on, and switching between a 4G or 5G network and Wi-Fi.
Accessed 2026-10-21.
LINE Help, checking or changing your phone numberhelp.line.me
The registered number is shown in Account settings on the main device. LINE says you can change that number only if you are using LINE in Hong Kong, Japan, Korea, Taiwan, or Thailand, by verifying the new number with a text message or a phone call. One mobile number can verify only one LINE account. Registering a number already on another account may make the original account inaccessible. LINE says you cannot change the number for 24 hours after transferring the account.
Accessed 2026-10-21.
Apple Support, iMessage, RCS, and SMSsupport.apple.com
iMessage can be sent to another Apple device over Wi-Fi or cellular-data networks and appears in blue bubbles. If Wi-Fi is unavailable, iMessage is sent over cellular data, and cellular data rates might apply. RCS needs iOS 18 and a text-messaging plan from a carrier that supports RCS. SMS and MMS need a text-messaging plan. RCS and SMS/MMS appear in green bubbles and are carrier-provided. Apple says to contact the carrier. That page does not say which connection carries a green RCS, SMS, or MMS message.
Accessed 2026-10-21.
Apple Support, iMessage overviewsupport.apple.com
iMessage texts can be sent over Wi-Fi or cellular service. They do not count against SMS, MMS, or RCS allowances, and cellular data rates may apply. A blue send button means iMessage. A green send button means SMS, MMS, or RCS.
Accessed 2026-10-21.
Apple Support, activate iMessage or FaceTimesupport.apple.com
Signing in needs a cellular data or Wi-Fi connection. On an iPhone, activating the phone number for iMessage and FaceTime needs SMS, and the carrier might charge for that SMS. An email address can be used instead, under Send & Receive for Messages and under You Can Be Reached By FaceTime At for FaceTime. If the number still has no check after 24 hours, Apple says to contact the carrier about international SMS. FaceTime is not available in all countries or regions. On a new iPhone set up with iOS 26, iMessage does not activate automatically if you add an eSIM in Settings later without having activated iMessage or the eSIM during setup.
Accessed 2026-10-21.
Apple Support, phone number in Messages or FaceTimesupport.apple.com
To set up a phone number for Messages or FaceTime, you need an active SIM or eSIM associated with that number. On the iPhone, the number and the Apple Account are selected under Send & Receive for Messages, and in the FaceTime list of where you can be reached.
Accessed 2026-10-21.
Apple Support, use FaceTimesupport.apple.com
FaceTime can be used over Wi-Fi or over cellular on supported iOS or iPadOS devices, and data rates may apply. With a cellular data plan, FaceTime can be used without Wi-Fi on an iPhone 4s or later, on iPad Pro, and on iPad (3rd generation or later). FaceTime, Group FaceTime, or FaceTime audio may not be available in all countries or regions.
Accessed 2026-10-21.