I answered they hung up. I called back they didn't pick up. Answering service says the call is important to us and they will call back. Calling at 8.30 at night surely is illegal. I don't I'll call you when later at night and continue to call them just to piss them off

Answered the call then no reply for three ‘hellos’ before they hung up.

They rang, and the phone was dead silent when answered.

Rang once then hung up

I called back number (03) 9124 5678 rang once then gets disconnected automatically.