My old phone number is still linked to my FaceTime and I have no access to this number to de-register it!
My old phone number which I no longer have access to is linked to my Apple ID and I cannot de-register it from my account
iPad mini, iOS 9
Question marked as
Look in the Security section when signed in online. 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.