I called back number (03) 5640 2801 voice mail says the number I have dialed is not in service anymore.

I would personally love to know who owns the number so that the authorities can deal with it and stop the person

This number hangs up when answered, then when tried to ring back ,it says this number is not in service. .???

The number I was given by Optus when I set up a "new" mobile phone plan is a pre-used number.
I'm bombarded with texts and calls looking for the numbers previous owner.

This number is one such call.

this number calls and hangs up when I answer

RP Australia AGAIN... First on (03) 5640 2800 and now this number! harrassing calls constantly....week in week out and I dont give my number to just any one! I can only think that an online query has seen by number sold on with data!