i had an interesting call from one of these "you've won a trip" companies several years ago.
i pressed the button to claim my prize. when the agent got on the phone they asked for a credit card number to get the process started. then i played along like i was really excited and started to give the first couple numbers. then i said, "wait a minute. i'm giving you my credit card number but i don't know anything about you" and started pressing for a proper phone number and address. the agent actually started giving me the information, then the phone went dead. very suspicious.
now we just ignore these calls.