Short answer
If a Japan eSIM is installed and still has no data, the checks are the mobile-data line, data roaming, and an APN only when the installation instructions show one for that eSIM. Apple, Google, and Samsung publish the settings paths, and Wakamo stores any APN on the provisioned profile.
Fact table
As of 2026-10-20
Each claim names its source. The full source list, with the date each page was read, is below.
| Claim | Source |
|---|---|
| To choose the data line, Apple says to open the Settings app, tap Cellular, tap Cellular Data, and select the line. | Apple Support, travel eSIM data line |
| Apple says one number at a time can use cellular data. To change it, open Settings, tap Cellular or Mobile Data, tap Cellular Data, and tap the number. | Apple Support, Dual SIM data |
| Apple says that if Allow Cellular Data Switching is off, cellular data does not work during a call on a number that is not the cellular-data number. Apple also says that automatic switch does not work while Data Roaming is on. | Apple Support, Dual SIM data |
| On an iPhone with Dual SIM or Dual eSIM, Apple says to open Settings, tap Cellular or Cellular Data, turn on Cellular Data, tap the number to change, tap Cellular Data Options, and turn on Data Roaming. On a single SIM or eSIM, Apple says to open Settings, tap Cellular or Cellular Data, turn on Cellular Data, tap Cellular Data Options, and turn on Data Roaming. | Apple Support, data roaming |
| If the status bar says No Service or SOS only, Apple says to turn Cellular Data on and make sure Data Roaming is on for that line. Apple also says to turn Airplane Mode on for about 30 seconds, turn it off, and let the iPhone select a network. If the date or time is wrong after arrival, Apple says to open Settings, tap General, tap Date & Time, and turn on Set Automatically. If service is still down, Apple says to contact the carrier. | Apple Support, data roaming |
| Apple says the APN defines the network path for all cellular data connectivity, and that you can view or edit it only if the carrier allows it. The paths are Settings, then Cellular, then Cellular Data Network, and Settings, then Mobile Data, then Mobile Data Options, then Mobile Data Network. Apple says not to edit the APN unless the carrier or a device administrator directs it. If you enter an incorrect APN, you might lose cellular data connectivity and receive additional charges. | Apple Support, APN |
| On iOS 16 and iPadOS 15 and later, Apple says a carrier that supports it can fill APN settings after the eSIM is set up: open Settings, tap Cellular, then tap Cellular Data Network. If you do not see the option to use the carrier settings, Apple says to enter the APN settings. If the iPhone has neither Cellular Data Network nor Mobile Data Network, Apple says to contact the carrier. | Apple Support, APN |
| On a Pixel, Google says to open Settings and tap Network & internet, then SIMs. Mobile data turns mobile data on or off. Roaming lets the phone send data over networks from other carriers when you leave an area your carrier covers. Under Your primary SIMs, Mobile data chooses the data SIM, and only one SIM can be the default for data. Google says these options vary by phone and Android version, and that some steps work only on Android 11 and up. | Google Pixel Help, mobile networks |
| Google lists Access point names on that Pixel SIM screen and describes them as helping the carrier find the right IP address for the phone and connect the phone securely. The same list includes Network, to pick a network operator from available networks. | Google Pixel Help, mobile networks |
| If Pixel mobile data fails, Google says to open Settings, tap Network & Internet, then SIMs, make sure Mobile data is on, tap the carrier name, and make sure Use SIM is on. Google says to turn airplane mode off under Settings, then Network & Internet, and to turn Wi-Fi off to read the signal. If those steps do not restore data, Google says to contact the carrier about outages and the data plan. | Google Pixel Help, fix mobile data |
| Samsung says that when you leave the area your carrier covers, you may still reach mobile data by turning on Data roaming, and to contact the carrier first because extra charges are possible. The path is Settings, Connections, Mobile networks, then the Data Roaming Access switch. Samsung says the screens vary by wireless service provider, software version, and phone model. | Samsung, Galaxy data usage |
| For an eSIM, Samsung says to open Settings, tap Connections, tap SIM manager, and turn on the switch beside the eSIM. Primary SIM sets the default for calls, texts, and data. Samsung then says to open Mobile networks, tap Access Point Names, and confirm the carrier, then tap Network operators and turn on Select automatically. If mobile data is still down, Samsung says to restart from the Quick panel with Power, then Restart, and to contact the carrier if it is still down. | Samsung, Galaxy data usage |
| Samsung says that if the Data Roaming switch is greyed out, turn Mobile data on under Settings, Connections, Data usage. If there is still no mobile data abroad, Samsung says to check that mobile data and data roaming are both on, that the provider has allowed roaming for the device and plan, to update the software, and to reboot. If it is still down, Samsung says to contact the network provider. | Samsung, Galaxy data roaming |
| Wakamo help says to check the APN if one is provided, and to follow the installation instructions. If mobile data is unavailable, it says to check the selected line, roaming and coverage, then the APN in those instructions. Menus may be managed by the carrier. If you still need help, the page lists [email protected]. | Wakamo help |
| A Wakamo Japan plan page does not list an APN. There is no single APN for every Japan plan. | Wakamo Japan plan page |
FAQ
Which line should use mobile data?
Apple says one number at a time can use cellular data: open Settings, tap Cellular or Mobile Data, tap Cellular Data, and tap the number. On a Pixel, Google says only one SIM can be the default for data, under Network & internet, then SIMs, Your primary SIMs, Mobile data. On a Galaxy, Samsung says to turn the eSIM on in SIM manager and use Primary SIM for data.
Where do I turn on data roaming?
On iPhone, Apple says to turn on Data Roaming under Cellular Data Options for that line, including when the status bar says No Service or SOS only. On a Pixel, Google lists Roaming on the SIM screen. On a Galaxy, Samsung says to turn on Data Roaming Access under Settings, Connections, Mobile networks, and to ask the carrier about extra charges first.
Do I type an APN?
Type one only when the installation instructions show an APN for this eSIM. A Japan plan does not list one APN for every plan. Apple says to enter an APN only when the carrier or a device administrator directs it, and only if the phone shows an APN menu. If the iPhone has neither APN menu, Apple says to contact the carrier.
What if the iPhone says No Service?
Apple says to turn Cellular Data and Data Roaming on for that line, turn Airplane Mode on for about 30 seconds, turn it off, and let the iPhone select a network. If the date or time is wrong after arrival, turn on Set Automatically under Settings, General, Date & Time. If service is still down, Apple says to contact the carrier.
Will a restart or airplane mode help?
Samsung says to restart a Galaxy from the Quick panel if mobile data is still down, and to reboot if data roaming abroad still fails. Apple says to use Airplane Mode for about 30 seconds and then let the iPhone select a network. Google says to turn airplane mode off on a Pixel and to check that Mobile data and Use SIM are on.
Who do I contact if there is still no data?
Apple and Google say to contact the carrier. Samsung says to contact the carrier, and on the roaming page to contact the network provider. Wakamo help lists [email protected].
Sources
Apple Support, travel eSIM data linesupport.apple.com
To choose the data line, open Settings, tap Cellular, tap Cellular Data, and select the line.
Accessed 2026-10-20.
Apple Support, Dual SIM datasupport.apple.com
One number at a time can use cellular data. If Allow Cellular Data Switching is off, cellular data does not work during a call on the other number. That automatic switch does not work while Data Roaming is on.
Accessed 2026-10-20.
Apple Support, data roamingsupport.apple.com
Data Roaming lives under Cellular Data Options for the line you change. No Service or SOS only uses the same check. Airplane Mode for about 30 seconds, then let the iPhone select a network. Set Automatically if the date or time is wrong. Contact the carrier if service is still down.
Accessed 2026-10-20.
Apple Support, APNsupport.apple.com
The APN is the cellular-data path. View or edit it only if the carrier allows it. Do not edit it unless the carrier or a device administrator directs you. On iOS 16, a carrier that supports it can fill the settings. If that carrier-settings option is missing, enter the APN. If neither APN menu is on the phone, contact the carrier.
Accessed 2026-10-20.
Google Pixel Help, mobile networkssupport.google.com
Settings, Network & internet, SIMs. Mobile data, Roaming, the primary data SIM, Access point names, and Network. Options vary by phone and Android version. Some steps work only on Android 11 and up.
Accessed 2026-10-20.
Google Pixel Help, fix mobile datasupport.google.com
Turn Mobile data and Use SIM on, turn airplane mode off, and turn Wi-Fi off to read the signal. If data is still down, contact the carrier about outages and the data plan.
Accessed 2026-10-20.
Samsung, Galaxy data usagesamsung.com
Data Roaming Access under Connections, Mobile networks. SIM manager and Primary SIM. Access Point Names, then Network operators with Select automatically on. Restart from the Quick panel. Screens vary. Contact the carrier if data is still down.
Accessed 2026-10-20.
Samsung, Galaxy data roamingsamsung.com
A greyed-out Data Roaming switch means Mobile data is off. Abroad, check mobile data, data roaming, provider permission, and a software update, then reboot. Contact the network provider if it is still down.
Accessed 2026-10-20.
Wakamo helpwakamo.io
Wakamo product information. If an installed eSIM has no data, check the APN when one is provided and follow the installation instructions. If mobile data is unavailable, check the selected line, roaming and coverage, then that APN. Menus may be managed by the carrier. The page lists [email protected].
Accessed 2026-10-20.
Wakamo Japan plan pagewakamo.io
Wakamo product information. The Japan plan page lists plans for sale and does not show an APN. There is no single APN for every Japan plan.
Accessed 2026-10-20.