I like the Sienfeld move, just tell them you are busy and ask if you can have their home number so you can call them back. When they tell you they can't give out their home number, then you say, "oh you don't like people bothering you at home either".
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Also, Jah, I agree..the seinfeld one is classic also. Here it is:
YouTube - How to respond to a telemarketer - The Seinfeld way