I am an exchange student from Hungary. I would like to buy an iPhone 5, but I don't know that I can use it in Hungary or not? An d how much money if I buy one with an American service? Can I change the service when I go back home or can i use with my American service in Hungary? And then I will pay the same or more? I have already an American phone and phone number(service Version) but it is just an basic phone.