I don't have a home phone anymore, but when I did, in the days before caller ID, we got them all the time. I learned to let them get out a few words, and then I'd say, "Thank you, but I'm not interested." Click.
Before I learned the few-words-thanks-click method, I would sometimes get drawn into the spiel; once, it was with someone from a long-distance company, and it was basically the conversation that made me decide to start hanging up on them, it made me so mad. The conversation went like this:
Telemarketer: Hello Ms. quiet_you, I see that you're with Company X.
quiet_you: Yes, I am.
T: Are you happy with Company X?
Q_Y: Yes, quite.
T: Well, did you know that if you switch to Company B, you'll save a lot of money?
Q_Y: No, I wasn't aware of that, but I'm very happy with Company X.
T: So you're happy spending a lot of money?
Q_Y: No, I just like Company X. I'm happy with them.
T: Well, if you want to spend a lot of money, which you apparently do, then you should stay with them.
AND HE HUNG UP ON ME.
And after that, It never went past "Hello, I'm calling from _____--" "Thank you, but I'm not interested." Click.
My best friend and I used to live together, and one day she decided she'd contribute money to the policemen's ball. AND SHE DID IT UNDER MY NAME. I was FURIOUS. I told her that if she ever did that again, I'd kill her. Every year, for the next 4 years, they'd call me and ask if I wanted to contribute money. And I'd say no, not this year. Sorry.
And when I moved out on my own and got a new phone number, they found me. And called. A couple times in a week. "No" every time.
Finally, on the third and final call in a week, someone called and asked if I wanted to contribute to the policemen's ball. And I did not mess with them. I did not offend them. I told them the truth.
Telemarketer: Ma'am, would you like to contribute to the policemen's ball? You've contributed in past years, which we appreciate, and we'd like to know if you'd like to contribute this year.
q_y: I'd be happy to. Unfortunately, I got a speeding ticket a few months ago for going 65 in a 55 zone on the interstate. I didn't slow down in time enough, and I was issued a ticket. While I have learned my lesson, this has caused my insurance to skyrocket, and I don't have a lot of extra money right now.
T: . . . Um, thank you, ma'am. Have a nice day.
q_y: You too!