What phone can I use? (T-Mobile ToGo)
From HowardForums Wiki
Basically, you can use any GSM phone that includes the 1900 band as a minimum since this is the band T-Mobile USA currently uses. It is recommended that you get a phone with both 850 and 1900 due to roaming. Your phone must either be T-Mobile branded or unlocked.
Source(s): T-Mobile solutions