Thanks leejosepho. I didn't realize that about the identity questions on the phone. Though I've had enough experience with debt that I should have caught on. It's good to have this tip on identifying what kind of call you're receiving.
Another ploy is for a credit card company to serve you with a court summons. It's actually illegal for a credit company to say they're suing you, if they aren't. I think you can get, like, an automatic judgement against them for that, giving you a thousand dollars they have to pay for doing that. But Barclays bank did that to me. People came to the door twice serving me a summons. Turned out it was just a ploy. They never pursued doing anything at all. An awful lot of what credit card companies and collectors do is a bunch of bluffing. But ordinary people don't realize that.