An Optus spokesperson said there had been “an issue involving a mobile phone tower site” in the Dapto region.
The outage affected calls between 3am and 12.20pm yesterday, including nine calls to the emergency hotline.
Optus said all people who attempted to contact triple zero were “okay”.
Several of the emergency calls were accidental or test calls.
About 4500 people were affected by the outage, but the Optus spokesperson said services had been restored.
The weekend outage comes just days after a major outage earlier this month that has been linked to multiple deaths.
Hundreds of emergency phone callers were left unconnected across multiple states.
Optus chief executive Stephen Rue blamed that outage on human error, saying a firewall upgrade had been botched.
“Initial investigations revealed that during the first night of the upgrade, the usual procedures followed in previous successful upgrades of this type were not adhered to,” he mentioned last week.
“On this occasion of the upgrade of 18 September, the first step in the process was not followed.”
Communications Minister Anika Wells has warned of “consequences” for the telco giant, but no specific penalties have yet been handed down.
