Caribbean number, don't call back. It could be a hoax. An oldie but goodie called the “one-ring scam” is gaining momentum again and leaving people with fraudulent charges. As independent analyst Richi Jennings points out, the scam takes advantage of a part of the North American Numbering Plan that gives three-digit area codes to certain Caribbean countries. People can connect to these numbers from U.S. phones that don’t have international calling plans even though they are actually “premium rate” numbers.