I suspect that this is a spoofing call - allowing the scammer to deliberately hide their number and display a different (often Australian) number.

Caller: Austra Energy

Did a quick Google search and this is what came up ... "Austra Energy" is not a recognized energy retailer in Australia. It's likely a scam or a phishing attempt. EnergyAustralia has received reports of scams impersonating energy companies, and they advise customers to report any suspicious emails or calls. BLOCK!

Typical scam caller, no actual response when you answer the call and don't speak they automatically hang up. Just another number to add to the blocklist