I am not quite sure why you are asking about a sim card. USVI is part of the USA network. Cell phone rates and service are no different than if you were still in the states. I could be wrong but I have ATT service and there was never anything different with my bill when on St. John. Connections and service was great, just as if I was standing next door to my neighbor back in PA. Puerto Rico, St. Thomas, St. John, St. Croix - none are "international". If you plan to visit the BVI, Tortola, Jost, that's a different story and those calls are considered international ones.