Cant deregister old phone number from imessage and facetime

See if this helps.

Remove your phone number

If you don't want calls or messages for your iPhone on your iPad, iPod touch, or Mac, you can remove your phone number. There are two ways to do this:

• On your iPhone, go to Settings > Messages > Send & Receive. Select your Apple ID and tap Sign Out. Then go to Settings > FaceTime, select your Apple ID and tap Sign Out.
• If the phone number that you want to remove belongs to an iPhone that you can't access, change your Apple ID password. This removes all phone numbers from your iPad, iPod touch, and Mac. Calls or messages for the removed numbers won't appear on those devices anymore.

If you have questions, contact Apple Support.

Turn your phone number on or off for your Mac

After you set up your phone number, you can turn it on or off for Messages and FaceTime on your Mac.

1. Open Messages or FaceTime. If asked, sign in with the Apple ID that you're using with Messages and FaceTime on your iPhone.
2. For Messages, choose Messages > Preferences, then click Accounts and select your iMessage account. For FaceTime, choose FaceTime > Preferences, then click Settings.
3. Turn your phone number on or off:
   • To turn on your phone number, select it and your Apple ID in the list. If you don't see your phone number, get help with your settings or contact Apple Support. If you see a number that isn't yours, change your Apple ID password.
   • To turn off your phone number, deselect it in the list.

FaceTime and iMessage - Link your phone number and Apple ID for use with

Have you changed it at the link below? Then try signing out of Messages and back in.

Apple ID - Manage