Missed a call from this number. Tried to call back but got message that it was not connected

Claimed to be checking eligibility for some government tax rebate thing, asked if I was under 59 and a home owner. I told him it was bollocks and to bugger off

Called answered then laughed at me and hung up

No answer nor reply. Just sounds like in a public place before they ended the call.

caller identified himself as a statistician asking about my age and my employment status and if I was renting or owned property.

Keeps ringing. I just don't answer, as I do not know anyone from this number. Ignore!

Supposedly from DURAL, NSW - if a missed call and trying to call back, its disconnected or invalid phone number. They will call you again and if you answer it, an indian call centre will talk to you about house investment and if you are just renting he hangs up the phone...

I have received several calls from (02) 9651 1657 this morning, but no you speaks.
I have tried calling the number back several times but get busy.
What is going on?

Called once and I answered, claimed to be a Not for profit org or something, I cant remember the name they used, they hung up when I questioned them. Missed call again a few days later, tried to return call and number is disconnected. Highly likely to be a scam.