Got a call from this number, I picked up but nobody spoke. After a couple of seconds they hung up.

Had 2 calls to my landline, and 2 to my mobile all with no message!

who was it

This number belongs to the guys at Etax

Keep getting calls form this number. Most of the time I miss them, but whenever I do pick up they hang up immediately. I've called the number and there is a msg which begins half-way through. I think it says "Sydney call centre trying to contact you on behalf of a client" then simply beeps and the call is cut off.

got 3 calls from this number in past 3 days.  It is a marketing call centre trying to sell me wine.  Their auto-dial is really slow so by the time they can hear you (4 seconds) you've hung up.  They also had problems with their system automatically hanging up.