Telstra has been forced to offer customers another free day of data for a mobile service outage lasting most of Thursday night, just over a month after an "embarrassing human error" took out mobile, home phone and internet services Australia-wide.
Around 6pm on Thursday a flood of complaints started appearing from users unable to access their mobile voice and data services.
"We are aware of an issue affecting some of our mobile customers who are having difficulty making and receiving calls, and using data," a spokesperson said at the time.
"We are looking into the cause of this issue and apologise for the inconvenience this is causing. We are doing everything we can to restore services as soon as possible."
Problems were reported from cities and towns nationwide. Telstra's service status page indicates issues with 4G, 3G, and 2G voice and data services.
The outage also appeared to be affecting corporate customers.
The VLine Geelong train line Twitter account said it was anticipating delays on all lines due to the Telstra fault, which was affecting all trains.
At around 9pm, three hours after the problems surfaced, Telstra said it was progressively restoring services and expected to return to normal "soon".
The telco continued advising customers services were progressively being restored until around 630am Friday morning.
A Telstra spokesperson early on Friday said an unspecified problem had triggered a "significant number of customers to be disconnected from the network".
"Reconnecting them caused congestion," the spokesperson said.
"We had a connection problem overseas impacting international roaming customers which then had a flow-on effect domestically."
The telco said it had commenced a major review of its network to understand how the issue occured.
It will offer free mobile data to all its customers on April 3 as an apology for the outage.
Customers are voicing anger with the telco over the repeat of a similar outage just over a month ago, which saw mobile, home phone and internet services downed for three hours as a result of human error.
The telco later confirmed the issue occured when a non-functioning node was taken down, but restarted before customers had been transferred elsewhere.
The outage forced the telco to offer its customers a free day of data the following Sunday as an apology for lack of services.