T-mobile work on ATT?

you mean 6t ? 6 wasn't sold through TMobile. I have the 1+6 not T and it's unlocked
 
According to the specs, it should. If you bring it into an AT&T (company owned) store, they can pop a SIM into it and find out for you. It's the least they can do to gain a customer. But there are no 4G bands that AT&T uses that the 6T is missing. (Even the 6 has Band 71, which TMO is using in some markets - and AT&T isn't.)
 
According to the specs, it should. If you bring it into an AT&T (company owned) store, they can pop a SIM into it and find out for you. It's the least they can do to gain a customer. But there are no 4G bands that AT&T uses that the 6T is missing. (Even the 6 has Band 71, which TMO is using in some markets - and AT&T isn't.)

The only thing if he's talking about the 6t on TMobile make sure it's sim unlocked TMobile likes to lock them phones lol
 
Oh it has to be, because Firstnet uses AT&T. (Most carrier-branded phones are SIM-locked.)