That's awesome, except that's good jazz, you need to torture them. Play them some Zorn or something.
There are some great stories on the web of what to say to telemarketers -- yes, far beyond, 'can I call you back at your dinner time'. Things like:
"oh thank god you called, I was about to kill myself"
"I'm kind of busy right now, can I call you back...hey, you might know, do you think I clip the red wire or the blue wire?"
"whatever you're selling -- can I pay for it in food stamps? If so, I might be interested"
"do you have to get up in the middle of the night to pee? Frequently?"