As the fallout continues from the provider's catastrophic outage - linked to four deaths - chief executive Stephen Rue offered a guarantee Optus would not let a similar thing happen in the future.
His assurance came despite a barrage of criticism of Optus for failing to implement recommendations from a review into a similar national outage that crippled the network.
About a third of the 18 review recommendations stemming from the 2023 outage, which resulted in fines totalling more than $12 million, are yet to be implemented.
Speaking from New York on Monday, Prime Minister Anthony Albanese said while there would be an investigation into the incident, he believed Optus' behaviour was "completely unacceptable".
"There will be a proper investigation by the authorities, and the government has action at its disposal, but the immediate concern will be that investigation," he told ABC television.
"Find out the facts, exactly how this happened.
"We will await the proper facts and will take what action is necessary."
When asked if Mr Rue should consider his position as CEO, Mr Albanese said he'd be surprised if that wasn't already happening.
Early investigations into Thursday's incident appeared to show established processes were not followed, with a botched firewall update blocking hundreds of triple-zero calls from Optus customers in South Australia, Western Australia and the Northern Territory.
But Mr Rue leaned on an independent investigation into the incident when asked how Optus could be trusted in the future after failing to implement recommendations from the previous outage.
"We will do an independent review, we will make the facts public, and I can assure you, we will be implementing everything," he said.
"What I can assure you is that actions are and will be taken to ensure that this does not happen in future."
Former Optus chief executive Kelly Bayer Rosmarin resigned in the wake of the 2023 outage before Mr Rue took over in 2024.
Two customers contacted Optus call centres early on Thursday morning before the outage was fixed after more than 13 hours.
A review uncovered three more calls over the issue but "red flags" were not raised because call volumes were normal, Mr Rue said.
An eight-week-old boy from Gawler West, north of Adelaide, was among four deaths linked to the fault.
But SA Police said the outage was "unlikely to have contributed" to the boy's death because his grandmother immediately used another phone to contact triple zero after her initial call failed.
The other deaths included a 68-year-old woman from the Adelaide suburb of Queenstown, a 74-year-old man from the Perth suburb of Willetton and a 49-year-old from the Perth suburb of Kensington.
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