iPhone 12
I can't use my phone's internet connection
Solution 3 of 4: Data roaming is turned off
You can limit your data usage when abroad by turning off data roaming. You'll then not be able to access the internet using the mobile network when abroad. You can still use Wi-Fi even though data roaming is turned off.
Press Settings.
Press Mobile Service.
Press Mobile Data Options.
Press the indicator next to "Data Roaming" to turn the function on or off.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.