called and left a message of silence lasting for 20 seconds, and i could get thru to them when i called back.

Caller: Social Research Centre

I looked into them. They're a research company owned by the Australian National University (ANU). They list all their numbers on their website and this is one of them. They called to conduct a survey on behalf of the Tasmanian department of health. The DOH site confirms that the Social Research Centre is conducting the survey this year. They're legit.

Annoying call. I didn' answer it. I tend to refuse all calls from unknown numbers.

Another nuisance caller....

scam

Caller: Social Research Centre

Online marketing researchers

Luckily I missed this call, but chances are I wouldn't have answered an unknown number anyway, Pity this scum have caused us to no longer trust answering a phone call.

Didn't answer because it was marked as a spam call

Caller: Data collection company

Conducting surveys about "health and well-being". As the other person said seem to be data collection.

Caller: Social Research Centre

This number is for the SRC seems to be a data collection company

after reverse number searching - conclude highly likely spoofed / spam caller

They have called 2 times, never left a message.