You need to call AT&T and activate the global roaming/calling plan. Cant remember exactly what it is called, but they will know. I think it will cost you an extra $8/mo and you need to keep it for 2-3 months since the billing can be delayed. If I remember correctly, it will cut the cost of your phone calls by half, so if you make a few phone calls, it is worth it. When I first visited Belize, I had to take care of all of this as well. This was 2.5 yrs ago, so things may have change by now. Hope this helps. And come visit our cafe to say hello if you're in San Pedro.