Thanks Lenin1991, maybe I'll call T-mobile and check with them as our next trip is coming up and we would like to do some walking tours.
Good luck @dyrd1955 -- no need for a fancy phone, as long as it has reasonable support for the wireless spectrum used in the countries you're going to. Websites don't load fast, but they load...it's kind of like a 56k modem if you lived through that. The first thing to check is log in to the My T-Mobile website, click your name in the top right, choose Profile, then click Blocking, and make sure "Block International Roaming" is disabled.
When we were in Europe we just bought international SIMS and had Verizon unlock our phones. My wife got a SIM from a Hong Kong company called 3 and I got one from Orange, which is French. It works almost seamlessly, ecept that if you are calling someone in the states your new foreign number comes up and it can get confusing. Otherwise, the 3 cost $23 and the Orange, if I remember correctly, was about $45. I'd go with the cheaper one, though. There's little to no difference.