These "credit card customer service" callers are robo-callers. There is no logic or plan to their attacks, as is evident from the thousands of complaints here at 800notes and other similar sites.
Your Caller ID is your best defense. If you get a call with a name and/or number you do not recognize, do not pick up the call. HANG UP!
Do report such calls to the Federal DNC Registry and the FCC.gov DNC complaint site. Do read the accounts here at 800 notes under the forums about how spam/scam/phishing "monsters" are being identified and shut down.