This happened to my father, called offered a Walmart gift card with only a $2.95 transaction fee. My father hung up but they called back and threatened him because he let them spend time talking to him and he didn't give them his credit card information. They yelled and told him they had his bank information and would debit it anyways. These people are crazy.
The same happened with me. I'm pretty sure he was Vietnamese! He had my address with him already. Wonder how he got that ! I told him I'm not interested. He tried to insist which confirmed that something was definitely fishy! So since he doesn't have my CC info, I believe he won't be able to charge me! Wonder how many different numbers they can call from though ? And how many times would they care to try!?!? He got unpleasant when I threatened to report him. Jerks!