WARNING--BEWARE!! These callers are B I G credit card criminals, known as the card service scammers! Under NO circumstances, give your credit card number to to these lowlifes, or you will regret it forever!
I hear the best way to deal with these sorta scammers is report them to the "Federal Trade Commission ...! It is there job to investigate these situations, an let the proper authorities handle them ...! It could be considered racketeering, embezzlement, if any large amounts of money are involved, an making prank phone calls is also against the law in many a countries or states ...!