They can, i use to work for TSA Australia Telstra's 3rd Party Telecommunication Services Australia and at or during each call they can click opt out of calls and yeah THEY ARE LAZY TO CLICK TWO BUTTONS ON THE MOUSE

I called (02) 8087 3122 back and spoke with Justin. I reached Optus, telecommunication company. He is from the Philippines. He is not able to remove my number from their end and so he gave me a website where i can opt out from all telemarketing calls www.donotcall.gov.au. I told him i just want to be opted out from their list but he is not able to do it from his end.

Waiting for a call back from Optus but it disconnected shortly after I accepted the call

Waiting on a callback from optus but no one talked to me when I answered. Very strange

Didn't answer me either, I was waiting for their call

Recieved call from this number while waiting on an optus call back. When answered did not here anything, said hello a few times then I was hung up on.

Optus Customer Service.

Received a call from this NSW number. They didn't hang up when I answered but didn't reply to repeated "hello" either.