This one seems to be the one best as I can tell. RM 1096
Microsoft Lumia 640 XL Smartphone RM-1096 (Black, Dual SIM) #Lumia_640XL-RM-1096-Black - Expansys USA
GSM Network: 850 MHz, 900 MHz, 1800 MHz, 1900 MHz
WCDMA Network: Band 1 (2100 MHz), band 2 (1900 MHz), band 4 (1700/2100 MHz), band 5 (850 MHz), band 8 (900 MHz)
LTE FDD network: Band 1 (2100 MHz), band 17 (700MHz), Band 2 (1900 MHz), band 20 (800MHz), band 3 (1800 MHz), band 4 (1700/2100 MHz), band 5 (850MHz ), Band 7 (2600 MHz), band 8 (900MHz), band 28 (700 MHz), band 12 (700 MHz)
T Mobile uses band 4 and 2 for WCDMA and band 4 for LTE. This phone seems to have both.