Watchdog phone call

Today I got a phone call from "Watchdog" saying that there a was a purchase of something online that was suspicious. They said that the phone number was my number and that someone had entered a credit card number that had an expiration date of _______ (I don't remember). It was just crazy because I was pretty sure that I didn't purchase anything. I DON'T EVEN HAVE A CREDIT CARD!!! My mom told me that the person who purchased the item probably was a scammer or the person who called me was a scammer to get the real credit card number.