Telemarketers can be a pain in the ass (there is really no other way to put it) but responding in the wrong way can make the situation worse.
As an ex-telemarketer, I know first-hand what it is like to be on both sides of the call and trust me, telemarketing sucks for both parties involved. I worked for a small call centre in Cambridge called C.S.I. that specialized in collecting donations for charities like the New England Police Officers Safety Association. To this day I sincerely hope it was legitimate, though I now have my doubts (I was only 15 then).
So how do you get rid of telemarketers?