I had one poor gal on the line for a good 20 minutes. She had this rehearsed message and when she would get going I would interrupt and ask some stupid unrelated question. Then I'd stop and say something like - "but you didn't call to listen to me prattle on, now how can I help you?" As soon as she got going again, this time a little further, I'd repeat the interruption. Amazing how many stupid questions I can come up with.
Once I tried the "Hey Steve, I thought you'd never call back. WTF dude, are we on for Saturday or not? I refused to believe that the caller was not "Steve."
My most recent actually had me in a raging fit because the guy did not let up. I yelled my favorite phrase "WHICH PART OF NO DID YOU NOT UNDERSTAND????"
Now I am a private person, so I don't know what a business owner can do that does not make them look bad. I would like to think that a stern "I am not interested in doing business with your company. Thank you and please do not call back" should do the trick. You can always threaten to turn them in to the BBB.