Try an experiment, add a new number but make sure it's in without any spaces before the number. Also the links below may offer some additional info.
Edit, Contect protection on option may also cause this.
KB16416-User is prompted to press 1 to answer a phone call on the BlackBerry smartphone 0 2042556693
KB01889-"My Number - Unknown" appears instead of the user's number on the BlackBerry smartphone 0 2042556693