Phone rang a few times and hung up without leaving a message.
I called back on (02) 8660 0540 and there was a message saying "They called on behalf of Kids with Cancer Foundation Australia who are running a raffle...."

Caller: I don’t know

Not a number I recognise - no message!

Kids with cancer foundation

Charity, Kids with Cancer selling raffle tickets.

I don't answer but it can sometimes call 15 times a day for days on end then stops for a while. It has just started up again.

Rang 3x, only for a couple of rings before hanging up and immediately redialling back to back

Caller: (02) 8660 0540

Calling every day, unknown number. Suspect robo call

Suspect "robo-call" - rang 4 x then stopped, no message left. This is the usual pattern for robo-calls

Silent for 5 seconds and then disconnected.

They let the phone ring twice and hang up.