Optus will launch an independent review into a network outage which may have cost at least three people their lives.
The company's CEO Stephen Rue has repeatedly apologised for the infrastructure failure on Thursday that left people unable to reach emergency services and led to "immense additional distress".
Rue on Sunday confirmed that two more callers in NSW were unable to reach emergency services during the 10-hour-long outage.
The federal emergency services minister, Kristy McBain, has blasted Optus outage as "absolutely disgraceful".
"The fact that no state or the federal government was advised of this outage I think is beyond reprehensible and there has obviously been some significant impacts," she said.
'Clearly not good enough'
Rue told reporters on Sunday the company would introduce a "compulsory escalation process" when people report a failure to reach triple-zero.
The company is also looking to conduct an independent review into the network outage.
"At the time of these calls, there were no red flags for the contact centre to alert them to any live issues. This is, clearly, not good enough and we are implementing a new compulsory escalation process following any customer reports of triple zero failures through our customer call centre."
Rue confirmed that two additional callers on the NSW side of its border with South Australia were also affected by the outage.
"Welfare checks on these calls have been progressed by Optus and the New South Wales police and we are not aware of any further issues."
Authorities clarify number of fatalities linked to the outage
An eight-week-old boy from Gawler West, north of Adelaide, was among four deaths authorities had linked to the fault.
While the boy's family was impacted, police now believed the outage is "unlikely to have contributed to the death".
"The deceased boy's grandmother has told investigating police that she attempted to call 000 using her mobile phone when she was alerted to the fact her grandson was not breathing," SA Police said in a statement on Sunday.
"When her call was not connected, she immediately used another mobile telephone in the house and was successfully connected to 000."
SA Police said an investigation into the death of a 68-year-old Queenstown woman was "more complex", with work continuing to determine the impact of the outage.
The deaths of two Perth men, a 74-year-old from Willetton and a 49-year-old from Kensington, are also being probed over the fault.
Additional reporting by the Australian Associated Press.
