There is many things you can say to a telemarketer. One of my personal favorites is:

Telemarketer: Would you like to buy a….

You: I’m busy right now, can you give me your home phone number?

Telemarketer: We are not allowed to do that.

You: why? Because you don’t want to get bothered at home?

You: Now you know how i feel. (Hangs up)

This is my personal favorite. I saw it on Seinfeld and i thought it was so funny!

Try it yourself.