We have an old phone with an island sim card, and it works great for us. However, there is a reason to also sign up for the Verizon International Plan, even if you have an island phone. When we departed in December, our flight was delayed for six hours, causing us to miss our connection and get stranded in Miami for three days. There was no WiFi at the airport at that time (maybe still isn't?), and we were unable to get timely updates on the situation and make alternate travel arrangements for the rest of our trip. Had we had the international plan on our Verizon phones, we would have been able to use that data. We did purchase data for our island phone, but it didn't work, for some reason that I still haven't been able to ascertain.