Oh just to add, when things work normally the mother-in-laws calls show up as 'anonymous' and on less frequent occasions as this number (02) 8011 1215). Wife said that at times she has answered and no one was on the other end, which again fits in with what some of you have also said.

Had a call from this number so I called it back and it was a fax machine.

This number has called a couple of times and no one is on the other end of the line.  Called back and got a fax machine.  Really pissed as i have a baby who goes down to sleep at around the same time this number calls.

I had a call from this number (02) 8011 1215, they left a message which was so garbled I could not understand it, like the phone was accidently dialed and people were talking in the background. I have not given my number to anyone in NSW (02), or anyone overseas (refer to Mike). A google search resulted brought me to this chat page. Its a puzzle.

we keep getting phone calls from this number.  we will soon report it to the authorities

My wife asked me about this number (after a missed call) and it looked like a call centre / survey type number. I told her sometimes you can get an idea by typing in the number (or a derivative) into Google search and getting lucky. Anyway this forum post was the top search item so I figured it was a call centre as all you people seemed to indicate the same thing. Tonight the number called back again and I answered and hung up immediately. My wife told me it could be her mum from overseas and to check for messages. I did and lo and behold it was my mother-in-law. It seems that sometimes her overseas calling card comes in via this number, so if any of you have people from overseas that call then perhaps check with them what time they called because it could well be them. Just thought you should know my experience because in my case it wasn't an annoying call-centre.