I have used the following script in the past
It works very very well!
By the time i get to the 5th question, THEY want to get the HELL OFF OF THE PHONE ASAP!
JUNKBUSTERS Anti-Telemarketing Script
``Are you calling to sell something?'' (or ``is this a telemarketing call?'')
``Could you tell me your full name please?'' $
``And a phone number, area code first?'' $
``What's the name of the organization you're calling for?'' $
``Does that organization keep a list of numbers it's been asked not to call?'' $
``I would like my number(s) put on that list. Can you take care of that now?'' $
``And does the company you work for also make telemarketing calls for any other organizations?'' (If they answer no, skip the next question.)
(If yes) ``Can you make sure your company won't call me for any other organization?'' $