Switching carriers, phone numbers, devices, and Apple IDs can certainly cause some confusion with iMessage. I switched service providers recently, and gave up my old phone number. In doing so, not only was my current number unlinked from my iMessages, but after some time, I was receiving someone else’s iMessages due to the old number being linked to my Apple ID!
Feeling lazy about it, I left it for quite a while and stopped using iMessage, and used my email address for it when I did. I eventually was too frustrated with the situation to let it go. A quick web search provided the result I needed.
(Special Note: You must be running a Mac with Messages installed, which comes standard in OS X Mountain Lion. If this isn’t the case, you can easily use someone else’s computer which meets these requirements.)
To change the Phone Number or Email Address associated with your Apple ID:
- Open Messages on the Mac and visit Messages > Preferences (command+comma).
- Click on the Accounts tab, and select the iMessage account.
- Click Add Email. (This step is not intuitive, as nothing about phone numbers is stated. Here you can also disable any email messages or mobile numbers you don’t want to use.)
- Enter the phone number you want tied to your Apple ID for iMessages. Make sure to include the hyphens.
- It will state, Validating next to your phone number, and then this will change to Email Sent. Your phone should receive a message with a link to confirm.
After confirming, your new number should now be tied to your Apple ID! Your iOS devices most likely will not recognize the change until you turn iMessage off and on in Settings on the iOS device.