NEWS YOU CAN USE: I'm a Telemarketer. Here's How to Get Rid of Me.
I have my own techniques: one, I just leave the phone unhung on a table without saying a word. I keep on with my life, and after a few minutes they loose patience and hang up. This worsens their time spent / effectivity ratio and they generally write it on their logs so that their colleagues know my number is not a good one to call. Since I'm doing it, telemarketing calls have gone down perhaps 60 or 70 percent.
Two, taken from Seinfield, and only if it's a nice, feminine voice: I reply, “sorry, I'm having dinner right now, why don't you give me your home or cell number and I'll return your call later?”
And three, when I'm fed up or in a bad mood: I reply, “sorry, can't talk right now: I'm cutting my grandma into pieces with a seesaw” or something like that. 9 out of 10 times they hang out immediately with no other word. The other one time, they hang up after saying “oh, sorry” embarrassedly.