Ok, my favorite thing to do is mess with solicition calls.

"Hold on a sec, gotta put my hearing aid in" I don't have a hearing aid "OK... (let him/her start spiel, wait 15 secs) "Oh hell, I gotta turn it on, wait a minute (mumble to self while doing nothing). "Ok, start over please" wait 20 secs "Dammit, hold on again, I'm sorry, I guess the battery died...can you speak up??"

Guaranteed the person on the other end either A) hangs up in frustration B) makes a butthead of himself by screaming into the phone.

If they do continue, doesn't matter what they are selling, keep asking silly questions to the caller - What time is it there? Was it hot there today? Do you guys get chairs or are you the operators standing by? Eventually they will hang up on you.

I cut down on about 90% of the calls I get by doing this.