I had received a lot of these calls from F.A.S.T., and finally the other day I decided to pick up the phone. It turns out to be from a group of police officers (I think highway police) collecting money. The pitch was in Spanish. They asked for my son (they said his name backwards - last name then first name), and I quickly told them to stop calling, that we were on the Do Not Call List. They also use other numbers (as mentioned in another response from August 2007).
GOT A CALL FROM 305-503-3522 3 TIMES CALLER ID SHOWS NO NAME WHEN I PICK UP THERE IS NO ONE THERE TRIED CALLING NUMBER BACK AND IT SAIDS
(# HAS BEEN TEMPORARY DISCONNECTED) *%%$@!