Messages and FaceTime stuck with temporary number

Question

I recently changed my provider and got a new phone number, temporarily, while my old provider transferred it. During that brief period of about 48 hours, my Apple Account, Messages and FaceTime picked up on the change and set everything to the new number.

Now I've got my old number back, I cannot seem to force Messages and FaceTime to pick up on the change back to my previous number. I have managed to add my old number back to my Apple Account and Trusted Number, but it insists on keeping that temporary number (which is now no longer in service) as the main contact for Messages and FaceTime, which subsequently appends it into my Apple Account.

I managed to get the above to work by switching iMessage and FaceTime off, then logging out of my Apple Account, and switching off; finally turning everything back on again about 20 minutes later. However, this has no effect on the Messages/FaceTime choice of contacts, which is stuck with that temporary number.

What's the trick to fix this?

(iPhone 8; iOS 13.2.3)

Answer 1

I managed to fix this by switching off Messages and FaceTime, removing the SIM, turning off, switching back on, reinserting the SIM and then manually tweaking the Apple Account contacts (removing the manually added number, which was a duplicate once the reinserted SIM was recognised).

I don’t know which of the above steps are necessary and which are optional, but it seems to have worked for me!