HOW DID THE OUTAGE UNFOLD?

* A firewall upgrade is initiated by Optus at 12.30am AEST on Thursday

* The upgrade blocks calls for Optus users in South Australia, Western Australia and the Northern Territory

* A customer calls the Optus contact centre directly about 9am to complain triple zero calls are not working

* Telecommunications Industry Ombudsman also refers complaints about the failure to Optus

* These calls were not handled "as would be expected", based on early review

* Optus becomes aware of the "severity" of the issue about 1.30pm after another customer contacts the company directly

* SA Police contact the company about 1.50pm to report triple zero calls are not working

* The upgrade is cancelled around that time and service is restored after more than 13 hours

WHAT HAS

See Full Page