how to put phone number for imessage
how do i add a phone number to select for imessage and facetime
iPad Pro, iPadOS 14
You need to change/add the number on your Apple ID. You may have to add the new number before you can remove the old number. After the change, allow up to 24 hours for the change to sync. Before trying to make the change, sign out of Messages/FaceTime on all devices/computers.
See the Apple Support article(s) below.