You can take the chip out and get an iPhone chip in Jamaica and use it there for local or top up enough and use the international plan, which is cheap. When you get back to states, switch chips. When your in the states or UK just top up online to your phone number. I usually email customer service, give them the required info and they tell me how many credits are on my phone. Get back to Ja and get a credit locally and your back on the phone again in Ja, remember to change the chip.