Which at least keeps them from scamming others for a while.
I have a fake cardstock credit card in my wallet from a magazine ad. I give them that number then when it doesn't work, I have a reference for when I say things like, "Oh, I switched two of the numbers," or, "That 0 is really a worn-down 8. My apologies." Normally it takes them 3 tries before they start cursing me out, but I kept one guy on the line for 30 minutes, and I ended it by saying, "Look. This has been fun and all, but I've been deliberately wasting your time, and I need to run an errand." I normally get cursed at, but one guy laughed and told me, "Good job!" and another genuinely sounded hurt that I would lie to him.
Best call was when the first guy handed me off to a "manager" because of problems with my account. I had already kept them on the line for five minutes.
Them: Hello, sir. I apologize for the inconvenience. Let's see if we can get things figured out. What is your last name?
Me: Not a problem. I hope you can help. My last name is Keyface.
Them: Yes sir, thank you, sir, Mr. Keyface. And what is the first name on the account?
Me: Don.
Them: Yes sir, thank you. So the name on the account is Don Keyface?
Me: Yes.
10 seconds of silence
Them: You motherfucking asshole.
Me: Figure it out, did you?
*Hangup*
Lately, I haven't had time to play so when I answer, and they ask how I am, I say, "Fine. Listen, I was having sex with your mother for money last night (I say it in more graphic terms), and she said that she's disappointed in what you do for a living." I then play random notes on my harmonica until they hang up.
Immature, probably doesn't make a difference, but I get some schadenfreude out of it.
TlalocW