I try to never be abusive or rude to telemarketers. Hey, they're trying to make a living and, if the only job they can find is one ringing strangers to sell something the stranger probably doesn't need, they're probably discouraged enough without my adding to the discouragement by losing my temper at them.
However, it's always acceptable to have a bit of fun with telemarketers while they're on the line.
Here are some suggestions. In each case, the goal is to encourage the telemarketer to hang up on you (and, then, to give him/her something to joke about with his colleagues during their tea break).
In each case, when the telemarketer asks for the manager of the business or the person in whose name the telephone account is in, say "Please wait a moment while I get him/her." This gives you a few moments to decide which of these strategies to employ.
1. When "the manager" picks up the phone, use the voice of The Swedish Chef from "The Muppet Show".
2. Otherwise, the "manager" can answer in the voice of Hercule Poirot (either the David Suchet or Peter Ustinov version). Ask plenty of questions (preferably detailed and pedantic) about the company. ("Which company handles your company's public liability insurance" is a good one. Don't forget to ask for the policy number.)
3. If you're feeling a bit naughty, interrupt the telemarketer to ask "What are you wearing?" Immediately follow this question up with (in your cheesiest possible voice) "Would you like to know what I'M wearing?"
4. "The boss" comes back on line with "Fraud Squad. Sergeant O'Halloran speaking."
For a long time, my favourite has been:
5. Interrupt the telemarketer's pitch with some totally irrelevant religious or political question, so that the telemarketer thinks he's about to be on the receiving end of an ideological or theological harangue. ("What you do you know about Scientology?" is a good one to use.)
My new favourite, though, is:
6. After the pause to get "the boss", get on the line with your best "disc jockey" voice: "This is Action FM, rocking the airwaves 24 hours a day. You're live and on the air. What's your Action FM Rocking Request?"
Try these, and you may probably find yourself with far shorter calls from telemarketers.
(However, you may find that you're getting the occasional repeat call from some companies as part of their initiation ritual for new telemarketers.)
In any event, you're helping to transform the telemarketer's call from a nuisance to (in W.S. Gilbert's words) "a source of innocent merriment".