Dealing With Telemarketers

I’m looking for a good way to deal with annoying telemarketers.  I’m on the national Do Not Call list, but I still receive lots of unsolicited calls that usually start with a prerecorded sales pitch, followed by an option to speak to a salesperson for more information.  The Caller ID information is usually unhelpful (a number I don’t recognize–probably fake anyway–with at best a vague description for the name).  Many of the calls seem to come from companies that sell leads to other companies.  The most common one is a credit card pitch, but there are calls from electricity providers and other companies, not to mention surveys (real and fake), charity solicitations (often claiming to benefit police or veterans), and of course political fundraising and campaign robocalls.  I usually stay on the line long enough to ask for the caller’s name, company, address, and phone number, but I almost never get a straight answer, and once they realize I’m not going to buy anything they just hang up on me.

I’m tempted to buy a cheap air horn, but I’ve read that call centers have shriek-rejection amplifiers that block loud noises to protect their employees’ hearing, so I’d just be wasting my money.  Yelling and swearing is sometimes cathartic, but after a day or two on the job, most telemarketers must be used to this, so I doubt it has much effect other than on my vocal cords.

Is there perhaps some kind of recorded hypnosis message I could play over the phone to get the caller to attack his or her supervisor, or at least to physically damage the call center’s equipment?  I understand that hypnotism supposedly won’t get people to do something that they wouldn’t otherwise consider, but you’d have to be a sociopath to become a telemarketer in the first place, so this shouldn’t be a problem.  Any other ideas?  (In case it’s not clear, I’m not looking for ideas like “just ignore them,” “don’t answer the phone,” or “ask them not to call again.”  I need something that makes the experience significantly more annoying for the caller than it is for me.)