Originally Posted by NJBlackBerry
Why unlikely, T-Mobile 3g is pretty much everywhere. 4G was a problem they are addressing.
The bands... There are some areas where T-Mobile has 3G on 850 and 1900, but it's not everywhere. 1700 is their most prevalent.
Originally Posted by rambo47
The 9780 supports T-Mobile's HSDPA 900 / 1700 / 2100 so as long as you have TMO 3G in your area you should be good. Best to speak to some local people who have TMO service to confirm 3G in your area. Don't trust carrier coverage maps as there are often gaps in locations in which they claim to have full coverage.
I'm pretty sure not all 9780s support 1700. I know even with the 9900 you had to get a T-Mobile branded one if you wanted 3G nationwide. Most unlocked versions sold on eBay will only support 850, 900, 1900, and 2100 3G/4G.
The OPs device box should say what bands it has.