My daughter has phone card from Sams. Love it here in the states. She wanted to call her boyfriend on our last cruise. She tried from Grand Caymen, Costa Maya & Cozumel & none would accept her card. She ended up paying $90 for about a 10 minute call. I had even called ahead to the phone card company & gotten island "codes" or "numbers" to use, but they did not work. She did not check when she called on a credit card from Cozumel & whatever long distance company it was really charged her! Luckily she is a saver & was able to pay me back.
In any event, I don't know the answer to your question, other than our phone card did not work at any of the above islands.