I have had the same experience as the previous 2 commentators. The number rings multiple times, doesn't leave voicemail messages, and hangs up if you pick up.

This number has continued to call me for the last few days, day & night. I obviously do not have number saved, so not family/friends etc. and have no reason for a Sydney based number to ph me. I'm getting pretty frustrated!

Received a call from (02) 9037 2804 this morning. She said she was from 24/7 and was ringing about insurance. I said I didn't need any and hung up. No idea how they got my mobile number, never heard of them before.

why do they keep calling, hang up too soon then search shows number is "unlisted""

This number is "24/7" an Insurance company based in melbourne they have also called me from (08) 7070 2532 as well. (Why they have numbers showing up with Sydney and Adelaide area codes I don't know. Is it a Scam?)