Currently I have a SPRINT US IPHONE 5 (unlocked) under a Sprint contract. I am traveling to Grenada (island) for a couple of months. In Grenada I am going to get a prepaid SIM which would gives me a new phone number. Would I be able to keep texting through my imessage SPRINT number if I have the prepaid sim card in the phone? So essentially I want to use my prepaid for everything, but I want to be able to text my friends in the US using my SPRINT US number that is tied to my apple ID.