I'm on another network, but I'm roaming on T-Mobile.Do you mean you're on T-Mobile and you're roaming on other networks, or you're on another network and you're roaming on T-Mobile?
Doesn't it depend on the agreement between your home carrier and T-Mobile? You're stuck with whatever they agreed to give you, which could be 2G.
Could be?However, during my trip to Japan earlier this year,while roaming on Softbanks network it was pretty much business as usual for us. I could use Google maps, text, watch youtube on the trains in the subways no problem 90% of the time. I would assume you will be roaming on either a 2g or 3g network per your carrier's roaming agreement with T-mobile U.S.? This is a ymwv kind of deal when roaming in a foreign country though.I could be completely wrong about this, but I think by default, foreign carriers' roaming customers are the lowest priority.