Still a gray area to do bussines with Cuba from the U.S., where most big VOIP operators are at. Some operations are outright ilegal on the eyes of uncle Sam.
Most South American countries had and still have PSTN links to Cuba. The U.S. companies,like ATT, still have the same ammount of lines that they had back on the sixties, when the embargo started.
Most VOIP to Cuba from the U.S. go trought South America, Mexico or China.
Good oportunity for you to resell service to Cuba from Chile.