Thanks for all your help. I went to a tmobile store, mentioned that I talked to customer service, all apn settings are correct. Have band 4 & 17 for lte, they put the latest model sim card in there and now I have lte @ 25 Mbps and 20 up.
I got my lumia 1520 unlocked yesterday thru att. I shows i have 4G. any reason i do not get lte in chicago? i set the apn, everything is working. i purchased a starter kit with nano sim, but it was a legacy sim. Should i change my sim? Thanks.