May 31, 2009
Your caller ID will say "CT" meaning Connecticut, where Mastercard is based. The caller will ask you to call back at a toll free number 888-333-0114
which is the anti fraud dept. I went directly to my Mastercard account and called the main number and listened to the voice prompts that asked if I'd been asked to return a call or letter regarding my account. After speaking to the customer rep about a transaction they thought looked suspicious, I asked about the above numbers and the rep verified those were legitimate Mastercard numbers. I'd still recommend dialing the numbers on your account transaction page or on the back of the actual card.