If you've got a spare computer lying around, and a few bucks for some parts from ebay, you could always build an
Asterisk phone system, and blacklist the telemarkers. I've got mine configured so that if a telemarketer calls, I hit a few buttons on my phone, it sends them to a recorded message that says "I'm not interested in your product, please remove me from your list", then disconnects them and adds them to a blacklist, so if they call again, it doesn't even ring my phone, they just get that message, and 'click'.