This is what worked for me…
I tried the suggestion of turning off iMessage and FaceTime and restarted the phone. I did this a few times but the number was still wrong on settings>phone>my number. I contacted Apple who advised me to go into settings>messages and toggle on imessage. Then go into send & receive. The wrong number was showing there so they asked me to hold it to delete it. I tapped on it and then held it but no option to delete. Then a second later it just changed itself to the correct number. Voila. Then I went and turned on FaceTime and all was good.
Also remember to check your number in Contacts under my card and also under settings>(your name)>name, phone numbers, email.
