The male caller, who had some kind of accent I could not identify, claimed to represent a body that could review my electricity bill and help me find a cheaper alternative to my current provider. When I challenged him to prove he was not a scammer, he acted really offended and told me (somewhat forcefully and at quite some length) that he was definitely not one of these, because was not after any of my personal or financial information.
Since he tried his absolute best to sound convincing, I wondered whether he had had acting classes. But, since he called from a Optus number that HAS BEEN DISCONNECTED, I am convinced that he is definitely a scammer! Beware!!

I called back number 0466 849 636 rang once then gets disconnected automatically.

no message left=block number

Called back number 0466 849 636, it says disconnected

I had a missed call from this number. When I return the call it says the number has been disconnected.

Called. No voicemail. Probably not with honest intent.

Repetitive call and no message left