Ring up your phone provider and get a trace put on your line, make note of the time of the calls from then on and after 3 hits, the provider will take action.

Further to my last post I found the following link, I think all this is saying though is it sounds link a generic number maybe that VOIP providers use for outgoing calls, so really it could be multiple customers using the same company for VOIP, even if this is a system outage fault notice.

http://www.adam.com.au/outages_system/outages-detail-2593.php

Network Status


AdamTalk Incorrect Caller ID for Private Numbers
Outage Type- Adamtalk
Impacted Customers- AdamTalk Customers With A Private Number
Impact Started- 9:00 Wed 6 May 2009
Impact Ceased- Ongoing
Adam Internet technicians are currently investigating an issue effecting customers with caller disabled, or have requested a private number. Customers may experience incorrect caller id when making a call. Instead of a Private Number, the number '(02) 8198 1100' maybe shown.

Calls will still route correctly, and audio is still correct, however, an incorrect caller id is shown.

UPDATE 2009-05-11 11:00: We are continuing to investigate this issue, and have escalated the case through our upstream provider.

these people are so annoying i want to call them and hang up like they do why is it when i try to call them back the message i get is the number you have called is disconnected how do they keep the same number everytime they call me even though it tells me the number is not in use?

Yeah I have had 6 calls from the number as well. just block it on your phone and forget about it.

yep just got a call from this number! so annoying as I've had this happen before with another number on my mobile!

I keep getting calls from (02) 8198 1100
It disconnects after 2 rings
When I try to call it back I'm told the number has been disconnected