The magic words to get a telemarketer off the phone are as follows:
“Could you take me off your calling list?”
It’s never failed me. Every telemarketer i’ve asked this of politely and immediately gets off the phone with me. These days, this is as close as I get to pure black magic.
In the US, they’re bound by law to comply, and if you want to go the extra mile, keep track of every time it happens. If they call you three times, there could be heavy fines in it for them.
I just wanted to share, since I know a lot of people probably don’t know this trick yet. 
I’ve never understood why people have a hard time hanging up on telemarketers, but here’s one for those who don’t have the heart:
Express a small amount of initial interest (a simple “aha” will typically do), then put the phone down (don’t hang up, just put the phone down) and walk away. The telemarketer will talk non-stop for the next 5 minutes, wasting his time and money, much as they try to waste yours.
Me, I just hang up the moment I recognize it’s a telemarketer.
Well, to be honest, sometimes on friends too….
Yeah yeah, doesn’t work like that in the UK, so I did a little more research…
My findings are currently located here: http://www.hm2k.org/articles/telemarketing.html
That’s an excellent resource. Thanks for the international info!
Indeed the same in the UK – if you ask to be taken off their list they do have to remove you. No-one likes getting telemarketing calls (which normally have no interest to you).