I'd have to admit, telemarketers are highly annoying.
The Tele-Zapper I heard, works like a charm.
I was also told by someone who works @ a telemarketting firm, that when you receive a call, and you notice that when you pick up to say "Hello" and you don't hear anything initially, it's probably a voice activated calling program. You have to say "Hello" the second time for it to prompt the telemarketer to rattle of their spiel.
She told me: if no one responds upon the first "Hello", hit the [#] on your phone 1 or 2X. It messes with their computerized dialing.
I have done this a couple of times, and it seems to have worked. I press the # key once or twice, then hang-up.
Recently I had a telemarketer who DID NOT/WOULD NOT listen.
I hung up on her.
"Is Mr. or Mrs...Dumbo there?" , "No, I killed them sorry".