That is the exact reason why I switched to T-Mobile. We are travelling internationally now and with no extra charges, it was a no brainer to change, plus it was cheaper.
Nothing like landing in a foreign country and when you take your phone out of airplane mode, the first thing that happens is you get a text from T-Mobile welcoming you to that country. I have welcome messages from Italy, Germany, Netherlands, Ireland, South Africa, the UK, France and Monaco telling me that I get data and texts at no cost while in the country. Calls however are 25 cents a minute.