Number called me on 19th July 2019 around 3.22pm AEST.
When answering no person spoke after requesting who was calling. then call was diverted to an automated answering system with a recorded voice message reminding me that I needed to pay my tax bill to ATO or face a visit by Police and subsequent court and legal action.
It then gave options to enquire further and be put into a queued call for discussion with a "service officer".
After eventually rotating through a queue for about 5 minutes eventually a male voice answered asking "what is your enquiry" to which I answered "well you people called me, and who exactly are you?" Then the call abruptly ended.
When calling the number back again I got a message that (02) 6521 3903 had been disconnected !

Subsequent enquiries on www.reverse.com show the following information :-

(02) 6521 3903 is a landline telephone number and it could be in Kempsey NSW or Lord Howe Island NSW or Muswellbrook NSW or Port Macquarie NSW or Taree NSW.

I later reported the matter on the ATO tax scam website :
https://www.ato.gov.au/reportascam/#reportscam