In case you haven't found it yet, Australian citizens are expected to opt-out of receiving telemarketing calls by going to
this website and registering phone numbers that they don't want to receive such calls at.
How does the register work?
Under the Do Not Call Register Act 2006, telemarketers can check their calling lists against the Do Not Call Register. If a telemarketer calls a number on the Do Not Call Register, they may be in breach of the Act, and may face penalties.
I firmly believe that it should be the other way around (ie. register if you
do want to receive such calls), but that would of course offend big business. As it stands, there's plenty of exceptions on there they can use to call you anyway.
Still, better than nothing I guess.