The numbers they call are not necessarily random. I was torturing one “reduce your credit card fees” guy by giving him 3 wrong credit card numbers in a row. He got mad and started threatening me with terminating all my credit cards - which was hilarious because just the moment before he was asking their numbers. But then to substantiate the threat he disclosed what knows about me. My address, my phone, my car make… the only thing they got wrong was my name - they used my son’s name instead of mine.

And other callers called me my son’s name a couple other times. So there seems to be some database that some of them share.