This number is not the ATO, but Probe Collections. If they say they are calling from the ATO, ask them if they are "from" the ATO or calling "on behalf" of the ATO? Debt collectors for the ATO like to blur the lines but make them admit they are actually from Probe, not the ATO.

Yes, just some outsourced debt collectors working for ATO. Hang up on them.

I called back number (03) 9021 6019 reached IVR for a company called The Probe Group.