Phone number
Why can't I add service to my phone all of a sudden? It's saying my phone number is invalid but has never changed since i got it.
iPhone 6s Plus, iOS 15
Question marked as
Go through the various suggestions in the support article below but if they don't help, and your network carrier can't help, then contact Apple Support for further investigation.
Support article:
https://support.apple.com/en-us/HT201415
You can also try this:
Settings, Messages, Turn off iMessage
Settings, Face Time, Turn off Face Time
Restart the phone.
Settings, Messages, Turn on iMessage, SMS, MMS
Settings, Face Time, Turn on Face Time