Possibly Card Member Services or Discover Account Services, but I do not answer when I don't recognize the number.

Been harassed by this scam group for years now. The only way to stop them is to continue to report them to the FTC/DNC/FBI, etc. If you answer (especially if it's a known scam number), they will continue to call you, possibly 4-5 times a day (this happened today after not responding to them for around 2 years).

Do NOT give them your information, they use phishing techniques to get your personal information such as name, address, and credit card number.