Adding minutes extends the time but once it expires you have to get a new sim with a new number. If all your numbers were stored on the old SIM keep it until you write them all down or transfer them to the phone (yes, I learned the hard way). I have used 2 different Cingular phones down there with no problems. The key is as listed above make sure it supports GSM 1900 and is unlocked. Some Cingular are only 850 and 1800. Tmobile is 1900. I only use it for calling around down there and it a lot cheaper than using Cingular's international plan. If you want to call back to the states an internet cafe is the cheapest way.