So I finally gave in and waited for an operator on this number. It turns out it's Open Universities Australia chasing previous students. This was after multiple calls from them over several weeks.

This number just rang then hung up when I answered

Have had numerous calls from (03) 8644 7418 but when we answer they hang up. Some previous comments by other people say they are Open University but I don't believe an organisation would behave like that. Someone should inform Open Uni that scammers are using their name

Have had several calls from this number with no message left. Put in queue when I returned call. Annoying!

Just had a call from them; answered but no one there.

I disabled my caller ID and called them back; a voice thanked me for calling back and to wait for an operator, but didn't identify which particular scumburger this lot was.

Same!! I never got a chance to answer when they called, it's clearly a
Melbourne number and seeing as though I don't live in melboure I have no idea why this person would be calling. Very strange that their "outside hours" recording does not state te company.

I had total 3 calls from this number 3 days in a roll. i didn't pick up and they just hang up, no message left.

Same as all above except I have not got as far as knowing who it is.  Only english voice etc.  very annoying.

Its open uni, trying to get students to sign up to commonwealth supported places to pay for uni fees. I signed up but they still call me.

Me too! I called them back and just was put in a queue, after a few mins it just went silent.