Hello Simonbambi,
Did you recently change numbers or wireless providers? We ask because this message you are receiving may be related to a change like that.
If you would like to use your number with iMessage, make sure to follow the steps here to add it to iMessage settings: Add or remove your phone number in Messages or FaceTime
- "Go to Settings > Messages and make sure iMessage is turned on. You may need to wait a moment for it to be activated.
- Tap Send & Receive. If you see "Use your Apple ID for iMessage", tap it and sign in with the same Apple ID that you use on your Mac, iPad and iPod touch.

3. In the "You can receive iMessages to and Reply From" section, make sure your phone number and Apple ID are selected.
4. Go to Settings > FaceTime and make sure your phone number and Apple ID are selected in the "You can be reached by FaceTime on" section."
We also recommend restarting your device and keeping it updated as those steps assure you have cleared out any minor software issues and are running the most current version.
Restart your iPhone - Apple Support
Update your iPhone or iPad - Apple Support
If you still have questions, reach out to Apple Support directly, as this may require closer guidance: Get Support
Cheers!