The t-mobile contracts with the international companies cover unlimited email only. It is the responsibility of the international company to submit your usage to T-mobile for them to bill you. So, I would argue that all of the free data usage is due to a lack of communication with T-Mobile and the international companies used while roaming.

In short this is Russian Roulette with your credit card.

I was lied to by every sales rep I spoke with until I chatted with a supervisor at 505-998-3793 .