You have to call T-Mobile and let them know you are going overseas. If you use your phone now the way it is your bill will be astronomical when you get back. I suggest calling T-Mobile and let them know that you want to get your phone unlocked so you can use another carrier's sim card in it they will normally take 48 hours to email you the unlock code. Once you have the code, purchase a sim when you get there and put it into the phone, use the code they gave you to unlock it. You will probably not have the same internet access you do here, however if you can use a wifi spot you will be able to get emails and the such.