I don't understand the compulsion to call back when scammers call you. Legitimate callers would leave a message asking you to return the call. If you do it with scammers, it only confirms that you exist as a target - and there are plenty of reports of calls to what appear to be local numbers actually going to overseas or "premium" numbers, at considerable cost. Please do as we've long been advised to do and do not answer calls from scammers.
This number and variants of it are currently being used by overseas scammers in another relentless barrage of scam calls in at least some of which they claim to be a charity. In the past week I have had attempted calls (the range of numbers is blocked) from (03) 9970 9611, 9625, 9628, 9629, and 9644.
I have made a report to Scamwatch about the calls evidently emanating from a fake charity.

Caller: Charity scam

Nuisance call, claiming to represent a multitude of charities. Avoiding do not call register or just "I don't give a fig".

No message left, scammer blocked.

If you’re not on my contact list and don’t leave me a message then you are another blocked number 😡😡

I keep getting calls from this number relentlessly

Don’t answer it

No message left- when I called back an Asian sounding voice (recorded) apologised that they did not have an agent available to take my call……. Blocked!

Didn't leave a message

Hung up on answering machine. Suspected spam.