I just got off a very obvious scam call where the scammer was offering to "lower" my interest rate. I played along to try to waste some of their time. I gave a fake expiration date and a fake last 4 digits of the card. He put me on a short hold and came back saying that was the wrong number. I went to a fake CC generator site thinking maybe there is something in the last 4 that can verify legitimacy kind of like the first four can indicate the Brand (Visa, MC, etc.). I gave him those last 4 and once again, after a brief hold, he came back saying it was the wrong number. At this point he lost his cool and started swearing, etc. and eventually hung up, but I've never heard or seen anything like this before.
Is it possible to verify that the last 4 digits of a card number are legit? In this case, it was supposed to be a Chase Visa. Could it be a checksum or something else? Might the expiration date and the last 4 need to match? Or is it more likely that he actually had my full number and was phishing for more info or something?