haha.
i'm a telemarketer.
*waits for the tomatoes to be thrown*
seriously though i make good money so i'll keep this job. i don't actually SELL, but more like do publicity for a company i won't name (but it's very well-known in canada, or at least the parent company is). we, as telemarketers, get annoyed by customers too. some are REALLY rude and it just ruins your whole day. there are ways to refuse politely.
here's how it works at my worklace:
if you say you are not interested, we WILL do a rebuttal until you say you are not interested again. after that, it's over.

if you answer and realize we're a telemarketer BEFORE we've introduced ourselves, WE WILL CALL BACK. TEN TIMES. so just plainly say that you are not interested OR wait for the introduction before hanging up if you don't want to be bothered again. we will also call back ten times if you never answer.
the reason why you would sometimes have to say 'hello?' a few times before we actually answer is because of the crappy computer systems, not because we are slow.

it is true that if you ask us to take you off the calling list, we WILL do it.
CURSING AT US WON'T MAKE YOU FEEL ANY BETTER.
in fact i've cried before because of really really rude and mean clients.

*weak heart* and i know it may get annoying, but i make sure to be as polite as possible so it'd just be nice if the other party did the same. ^^ have pity on us little ones trying to make a living.