My mom was getting some calls like that. Turned out the error was really quite simple: They had the wrong area code number, and probably also a couple other numbers switched around. Of course, this could also have been an intentional deception on the part of the mystery debtor. I forget who it was calling my mom, but it stopped as soon as we actually picked up once and there was a person on the other end to whom we explained that they had the wrong number. I think it was simple enough since the address they had clearly did not match the area code. Also, it wasn't AmEx. Sounds like that may have helped. So yes, if only for their own sake, AmEx needs to clean up their act here.

And I agree that OakLeaf probably has the right approach. Not that I'm a lawyer or ever played one on TV, but these don't seem to be simple marketing calls, so "get me off your list" probably won't help. AmEx has a right to call their own customers, even to repeatedly call those who are in arrears. But to do that they need to be sure of the number they're calling. And they'd be better advised to remain polite, but ultimately that's their own problem, as in: Thanks for the warning; I'll stick with the cards I have and not get entangled with AmEx, thank you very much.