I am trying to determine what I need to cross check if a particular phone will work on a particular carrier. The phone I am considering is the HTC ONE M9 or A9. In looking at the actual phone specs for the A9: 2G: GSM 850 / 900 / 1800 / 1900 3G: HSDPA 850 / 900 / 1900 / 2100 4G: LTE B1(2100), B2(1900), B3(1800), B4(1700/2100), B5(850), B7(2600), B8(900), B17(700), B20(800) The carrier I am using now is Simple Mobile, a T-Mobile MVNO. I looked up some reviews for this phone and some claimed that on T-Mobile is was not getting LTE but some other reviews say 4G works. Simple Mobile's web site says "To receive 3G/4G/LTE data speeds, make sure it has the 1700 or 1900/AWS band; otherwise, it will only work on EDGE." Does it mean it should support 4G LTE because the phone has LTE B1(2100) and B4(1700/2100) listed? I don't quite understand the B1, B2 etc terminology. If not, is there a HTC phone that works well with Simple Mobile?