Get $40 off a TrueCall Blocker (normal price $199.95).
From the TrueCall website:
Stop Nuisance Calls with the TrueCall Blocker.
TrueCall plugs into your telephone line at home and checks every call your receive before letting your phone ring.
It remembers who you like to talk to and who you don’t.
Friends are put straight through. Unknown callers are asked to identify themselves before TrueCall rings your phone and announces them. You then have complete control to accept, reject or send the call to voicemail. You can block all international callers or withheld numbers - the choice is yours.
I've had problems with nuisance callers. I repeatedly complained to Telstra but they couldn't do anything but pointed me to TrueCall. I've had it in a couple of weeks now and it's been great. No unwanted calls, but people I want to talk to get through straight away.
Have you ever heard of DNCR?