FYI, Update on Tmobile lie.
I do have a Post Paid account with Tmobile and it is false advertising, I went international and received a signal with Orange Cellular service at the country that I was staying, connected my device to the Wifi and thought that I was good to go, I had all the latest software on the phone, I even called them to tell them that I was traveling and were, they said that I will not have any issues on receiving or making calls for FREE as long as I was connected to WIFI, BIG LIE!!!!, they phone was never disconnected from wifi, I find this out after I get the big bill from them and they claimed that I was never connected to wifi, they even told me that if somebody calls you and you do not answer and it goes to voicemail, you still get charge $0.20 per minute. In all is is not worth the money, just buy an unlock phone and pick up a SIM Card from the local carrier, if there is a way to turn off the call receiving feature on the phone, do it, or tell your friends not to call you when you go out international.
I use it on the USA and it does not work, so it is a big ripoff.