Same thing just happened to me. They hung up straight away.

Did not answer. The number doesn't exist if you return the call. Scam!

called but didn't leave msg so figured spam - looks like that was the case

auto pre-qualification dialler. Hung up for later calling. Undoubtedly shady characters want to scam recipients

This number keeps calling me but they hang up when I answer

Caller: Pretended to be Telstra NBN security

Already scammed one of my friends to give access to her phone device so didn’t give them any info when they called.
I don’t even have Telstra but they pretend someone has accessed my NBN account and that they can help you. Just hang up and don’t give any info!