Best answer by Kevin
Could you go to Settings > [Your Profile] > Name, Numbers, Emails
and then ensure within there that the correct number is showing?
You may possibly need to log out of iCloud or Apple ID in order to make the change.
Another method that has worked in the past for others is as follows...
Turn off the iPhone > Take out your SIM
Turn the iPhone back on (no SIM) > Leave on for a minute or so.
Pop the iD Mobile SIM back in the iPhone > Turn back on.
This sometimes helps get the iPhone to refresh the information it's holding for your SIM and phone number etc.