Maybe I'm out of line, but you CAN text without your callback number. You hit the menu while in text messsaging and there is a place where you can disable the callback number being attached to any text that you send, or you can change the callback number, change or add a signature, etc.
just an FYI
Going back to disabling your call back number in the messaging settings, go to edit call back number, and delete it, make it blank. See if that works.
Sent from my DROID RAZR using Android Central Forums