The ability to roam onto a different network? Yes, T-mobile doesn't cover everywhere, but has roaming agreements to fill the gaps in coverage. There's a caveat

The ability to roam onto a different network? Yes, T-mobile doesn't cover everywhere, but has roaming agreements to fill the gaps in coverage. There's a caveat that data roaming is pretty restricted. My wife visited Bozeman, MT, and was limited to, I think, 10 megs of data, which went very quickly. On the other hand, in the UK T-mobile had unlimited but somewhat slow data at no extra cost.