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.
Find the best rate for calls to Cuba from your PSTN provider.Negotiate a deal by volume.
Find a internet service provider that could sell you bandwith to the internet, leased line or radio link. You will need 12 to 15 kb of internet for each channel of PSTN.
ON the PSTN or long distance provider, stay digital. Ask for E1 or fractional, but not analogs if you want to keep your hair.
After that you need a gateway, that will do the conversion from internet VOIP to PSTN.
Do not need a billing system ,since you will be selling “bulk”.
Contact a brokerage group, like IPCB.com where you coulf offer your minutes to others.
Make money, be happy.