Some companies pay marketers by the call, which is on record. You may find that the unscrupulous callers just want a call recorded and that is why there is no message left or no one answering if you call back. The call is recorded, counts and the marketer gets paid....
robo-diallers call a whole bunch of numbers in a row, and are supposed to transfer to a live agent, if they detect that a real human has answered. the only trouble is, if they don't have enough agents, or if the agent isn't ready, all you get is dead air. this is annoying for you, and a complete waste for the organization, but such is telemarketing.
wouldn't it be nice if all the charities decided that this was a waste of time, and just stopped using these telepests?