gdgt

I've never swapped SIM cards on unlocked GSM phones, so the whole concept still confuses me slightly. I’m currently off-contract on AT&T with an iPhone 3G, and desperately want to switch to an HTC G2 in October. I don’t want to sign up with a new contract, so I was planning on buying this phone from T-Mobile at full price and go with their off-contract plan. That is, until I found out that they do not off free data roaming (correct me if I’m wrong). I travel a decent amount away from Detroit in Michigan, and T-Mobile data in-network coverage of Michigan is atrocious. I had assumed that the frequency bands on the G2 would not cover AT&T’s 3G band. But it looks like it actually does, judging by the specs on T-Mobile’s and HTC’s sites. The G2 shows [GSM: 850, 900, 1800, 1900 UMTS: Yes], and going from the iPhone 4’s specs, [850/900/1800/1900/2100 (UMTS = 2100?)]. I interpret these specs as meaning that both phones cover the same exact frequencies.

So, here’s my question: In theory, will I be able to buy the G2 at full price, swap my SIM from my iPhone 3G into the G2, and use the phone on AT&T’s full network (EDGE talk and 3G data)? Of course I understand we probably can’t say for certain until the phone is in our hands to test this theory, but it would be great to know if my theory is even applicable in this case, before I buy the phone. I can certainly live with T-Mobile network, but I’d hate to watch my data usage when visiting rural Michigan.

Thanks in advance for any help you can provide!!