Seems to me that some time ago I got an e-mail telling how to discourage telemarketers. Every time you get one, I think it said to immediately punch pound and star, either both or one at a time, several times in a row. Supposed to foul up their computerized numbers they were supposed to call.
I've been trying to find this because of all the political calls I"ve been getting.
Or, simply tell them you know they are trying to make a living, but you never buy anything over the phone and hang up. Never argue or discuss your stand. Firm but not buying from them. Hanging up cuts into their profits.