Got the same call today and have gotten it before.  They've refused to identify themselves in the past and hang up on you when you ask about the do not call list or answer any of their questions in a manner in which they do not like (i.e., I don't carry a balance on my credit cards).  A call back to the number they called from gets the automated message, "The number or code you have dialed is incorrect. Please check the number or code and try again."

SPAM - ROBO CALL
CID: MELBOURNE, FL

Didn't answer.  Google the number.  Scammer.  Add number to reject list

Answered and it was silent.

They called to offer to lower ALL my credit card rates.  Asked what card and how they got my info and they hung up. Tried calling back and it says unable to locate. Scam