I also had a missed call on my Optus mobile from (02) 9027 8500 today.  I entered the number into google and found this thread.I later had a call from (02) 9027 8000 around 6:00pm (tea time), which I had noticed was also mentioned in this thread.  I was asked for three minutes of my time to be in a survey.  I asked what it was about and he said it was about my call to Optus yesterday.  Yesterday I rang Optus on 1300 555 002 regarding my prepaid mobile phone account.I asked if the survey was needed because the area I rang the day before was an area that had been outsourced.  He said yes.  I said hang on a second and when I finished cooking and eating my tea I checked my phone and he had hung up.

Hello my dearest Atbin
It is a surprize to see you here!
I have been looking for your contact details since you left iran,
by the way this is my Email: k_keshvarian @ yahoo.com
make me happy by keeping in touch
Yours
Kourosh

I got a call from this number today, claiming to Optus Research want to talk my mother who I swapped phones with over a year ago.  They were in a big hurry to get off the phone...

They actually called me 5 times when I am in Hong Kong - INTERNATIONAL ROAMING..lucky I didnt pick up the phone but they kept calling 3 times a day..man..

Had missed calls on mobile

I just received a missed call from this number. No answer when I rang back. I'm with Optus, could be them.