I called back number (02) 9099 1774 reached voice mail but did not say for what company.

Scam, recorded message requesting information supposedly for survey - questionable as to seeking personal information re: ID theft

"scientific survey" to get opinion of Malcom Turnbull et al. Robot leaves a message to call back, then commences the survey, when you return the cal,l using an automatic responder

Had 4 calls this afternoon, 2 at the same time?!
Starts off like a questionnaire about Malcolm Turnbull then goes into plebiscite questions..
My impression is that it's from the 'yes' camp trying to sway people's decision towards 'yes'.. Quickest way to get a big old 'F-NO!' out of me is to try and bully me to say yes.. wankers.

Spam call, sounds like recorded message in background then hangs up.

They called but hung up after one ring. They rang back a few minutes later with a pre-recorded message about being an intelligence service but it then cut out and hung-up. I'm not sure if this was an opinion poll / survey thing where there wasn't an operator available so it cut out or what it was, weird call either way.

Answered and no-one on other end.