While it is tempting to give these scumbags the business, it won't stop them but it will waste your time.
Mostly I don't have to deal with them. My landline phone provider has a pretty good call blocking feature. Once a number is input, when that number calls again they get a recorded message "The person you are calling is presently unavailable." Click.
If a new caller gets through because they are not yet in the system, I just use the old 'policy' statement. "I'm sorry but it's our policy not to respond to telephone solicitations." Click. Then, with a couple of buttons on the phone, that number too goes into call blocking.
Also, if we're watching TV, the incoming number appears on the screen. If we don't recognize it, we don't pick up.
