I called this number back and it says it from Contact Centres Australia. They said I would have received a miss call from them about a client's initiative.
They had called me and while I was putting on speaker I heard a voice but it just hung up on me.
I've never heard of them and I don't think I signed up for anything with them nor am I a part of any initiatives.
I think it was probably a scam or company wanting something from me and I don't feel I need to waste my time following them up.

I called back number (02) 8016 0400 rang once then gets disconnected automatically.