File a fraud alert with the credit reporting agencies and also get your credit card number changed. I think these people are credit card thieves. Since they can spoof your phone number, they can call your credit card provider and make it look like the call is coming from your phone. I think all they need is the last four digits of your credit card to access your account. That is one racket, asking for your card number is another. If you reported your card stolen, they should not be able to do anything with it and hopefully they will get caught when they try to buy something with it.
My new approach is to pretend interest and, when they ask for my credit card information, tell them I have to go find the credit card. Then I let them sit and wait while I work on the computer or do something else. In a couple of cases (after they've waited several minutes) I tell them I am on the Do Not Call list and never had any interest in their so-called service.
Received a call on my cell; didn't recognize it so I didn't answer it. No voice mail left, either. Right away checked it out on this site and I see that my instincts not to answer it were correct. Just registering another call from this number so others can see the pattern.
I have had the same thing happening for a couple of months now. I answered once and got the same response about a credit card. I started asking questions and they hung up. They are using a device that gives an anonymous telephone number. I have written down the number to the State Police and the next time they call, I am going to say I have bad reception and tell them to call me at my other phone number, then give them the number for the police. Most police stations get an accurate description from where the call is being placed from, and the anonymous number thing will not work.
Not sure if they will return a call or not, but I will take a chance.