When I upgraded my iPhone to iOS 6 yesterday, I never got the prompt to unify my Apple ID and phone number. Now I have no idea how to do it, since there's nothing about it in Settings.
If it's not listed, which it wasn't for me, disable iMessage and FaceTime on all of the devices. Then reenable it on the iPhone. After its been verified, activate it again on the other devices. Number should show up as receive and send options. May only need to disable on the iPhone. Not sure, but that is what I did and it worked for me!
Check out the solution from this thread.
http://forums.imore.com/ios-6-forum/240388-ios-6-messages-facetime.html