Your GSM phone with a BTL prepaid SIM will work on the local network. You will be able to receive calls for free (Int'l) for any length of time.
You will have a local number like 601-xxxx. From the US 011-501-601-xxxx.
Local calls can be made for $US.43 (max/peak) per minute.
Credit Card calls are free also.
Calls to the US are not cheap, but reasonable.