I've asked more than one of them how they sleep at night - but only after they've got aggressive with me, which happens surprisingly often. I was once accused of being a liar when I said I didn't have a Windows computer. Oh, the irony.

Most of the time I don't bother, I just hang up the phone, but if I'm in the mood I'll keep them hanging on by asking stupid questions - such as demanding they tell me their real name, because I doubt it is 'Keith' - until they hang up. I think of it as a public service. If they're on the phone to me, that cuts down the time they are calling more vulnerable people.