It may be against the rules, but since I am not selling anything….
Look for the ads on the forums about Charles Chang, with tmtelcomm.com , in Miami.
Not the cheapest carrier, but incredible stable and you could open an account with only $500, and go from there.
Weekely CDR, never had a trouble with them, even with extrange destinations.
Again, not a agent of this company, only a satisfied customer.
Also, never had a trouble with DUAL Talk, that was my first carrier. Could make payments via credit card on the middle of the night, online.
Once you are setup you could watch your calls online, make payments and change the I.P. addreses of the gateways allowed to send calls in your account.
You could even sell service to people that have a gateway ,but no account. You open or close the access whenever you like it.
Both companies are very responsive to e-mails, troubles, etc.