Customers first began noticing problems at around 4 am on Wednesday, with services gradually restored from around 1pm.
Customers and businesses were unable to connect to the internet or make or receive calls for close to nine hours.
Chief Executive Kelly Bayer Rosmarin also confirmed that during the outage Triple 0 calls could not be made from landline phones but were still possible on mobile phones.
The outage comes nearly a year after about 10 million customers had their personal details stolen in a cyber attack.
Bayer Rosmarin said there was no indication this outage was the result of a cyber attack.
The cause of Wednesday’s outage has not been revealed by the telecommunications company.
