There have been a number of credit card scams over the years. Typically, the scammer calls and provides you with a majority of your credit card information and requests one final piece of information. What the scammers want is the three-digit PIN number on the back of the card. Don't give it to them. Instead, call your credit card company directly for verification of the conversation.
If you give the scammers your three-digit PIN number, you have made it possible for scammers to make illegal purchases on your credit card. However, by the time you get your statement you'll see charges for purchases you didn't make and by then it's almost too late and/or more difficult to actually file a fraud report.