when answered, nothing for about a minute ,then an automated voice says "goodbye"
on returning the call I am informed that the number is not connected. interestingly, in a shot time after, I get a call from another Number, (03) 9028 2362 which according to this site is a tax scammer.

This number is repeatedly calling me, wont leave a message and when I try to call it back, it is not connected..........

Caller: Mark - or at least that was his alias.

Unsolicited spam callers using auto connect software, hence the delay. Just abuse them. They are worthless.

Who knows who called because the idiots obviously need to get a life. What on earth would the purpose be to keep ringing people and hanging up. Just goes to show the mentality of these folk eh? We should probably feel sorry for them.

I answered and they hung up, usual scumbags that do this.

On returning missed call - Optus message saying the number is disconnected

I called back number (02) 3056 8490 rang once then gets disconnected automatically.