It is a scam , DO NOT give them money. These are well-known scammers.
It was covered in
http://www.lotteryflorida.net
plus there was a programme on it, they will ask you for an initial sum and they ask for more and more to cover " costs " in order to release your money.
When they next call you, tell them to stick it up their a** just because you are from America it doesn`t mean you are that gulliable - they make me sick!!