I'll mess with them to see how long I can keep them on the line giving them a bad credit card number, which, whoops, I transposed these two numbers, try it again so I can get 0% interest. Still didn't work? Oh, my fault. That 0 is actually a worn-down 8, try it again. Normally after about 3 tries they realize I'm messing with them and start cursing me out, but recently one guy transferred me to someone else, and we had this conversation.
Scammer: Yes, what is the last name on the account?
Me: Keyface.
Scammer: Yes, thank you, sir, and what is your first name?
Me: Don.
Scammer: Yes, thank you sir... (5 second pause) You mother-fucker!
Me: Figure it out, did ya?
Scammer: <hangup>
Lately though, I haven't had time to play so I've been meaner and after the scammer greets me, I'll say something like, "Listen, I was fucking your whore of a mother last night, and she says she's disappointed in your career choices." Then I start playing my harmonica loudly into the phone while the person yells at me until they hang up. It's childish, but it's also oddly satisfying.
TlalocW