I used an AT&T calling card that I bought at Sams. There is a toll free number on the back to get dialing instructions. It worked in Cozumel, but not at Cayman. You have to use certains phones..I think Telnor, Latitex, or something like that...it tells you in the dialing instructions. I called before we sailed and got the international number. Then I taped it to the actual card. The card was a 150 minute card, but each minute of call used up 9 minutes of the card.