I used AAA to join the Advantage program last year and got the same notice to re-verify.
However, the site reported I am with BCD Travel... Even I uploaded 3 times the AAA membership card, I got rejected.
Called customer care and got bounced around telling me to dial a 877-aaa-7494 (888-222-7494) and the rep from that number don't know anything about it and tell me to call AAA directly and to figure it out myself.
Looks like Tmobile is trying to play around this reverify steps to get rid of the discount.
Why not just say it out straight rather than kicking people around like this!