Phone number not option for recieve at iPhone

Hi, I just unlocked my wifes iPhone4 through ATT.  She started using it again, now on ios 5.1, and when she sends an imessage to others her contact displays as her email address.  I looked into other posts and people sugested taking a look at the "Recieve At" options.  On my 4s I see both my phone number and an email, this is what most people are reporting.  However, on my wifes 4 ONLY email is an option, her phone number doesn't even show up and there is not an "Add a number" option.  Has anyone else run into these problems?  Maybe it has something to do with the new factory unlock?  Any help would be appreciated, thanks!