Default T-Mobile Note 3 on ATT APN problem

I have been using a SM-N900T on the ATT network by changing the APN settings, and it has been working perfectly until today. I have no internet connection, but it shows full bars, and I can still call and text. I've tried restoring to a earlier NANDROID, and even went to an ATT store and had the guy (who happened to know exactly what I did and has done it himself for his phone) try to fix it, but nothing has worked.

I posted this in the AT&T section too, but no luck so far. Any help is greatly appreciated.