Sounds like the number might be blank in Settings > Phone > My Number, @Bonobojim.
The online coverage checkers are just a theoretical prediction of signal strength at any given location - actual signal strength can be better or worse.
Perhaps try the iD online Live Chat for help. The advisers work until 8pm on weekdays - the iD chatbot works 24/7.
Tell the chatbot you want to “talk to a person”.
Aha, it is showing as blank - anything I can do that doesn’t involve a hour long wait on the live chat?
Okay @Bonobojim, I’ll assume you know your number, so try adding it yourself in the Settings app on your iPhone - starting with “+447” etcetera.
Once that’s done - restart your iPhone.
Hey there @Bonobojim, welcome to Community!
Please try the following:
1) Turn off iMessage (Settings > Messages)
2) Restart your phone (by pressing and holding the on/off button)
3) Tap Settings > Phone > My Number and confirm that it is correct.
4) If it is not correct, please enter the correct number
5) Turn iMessage back to On (Settings > Messages)
6) Finally, go to Settings > Messages > Send & Receive and see if the correct number is displayed under "Start new conversations from:"
If you are having issues with step 4 please reset network settings and try again.
Settings > General > Transfer or Reset eDevice] > Reset > Reset Network Settings.
Thanks,
Tyler