Following a network breakdown at telecoms giant Optus, millions of Australians have been left without mobile and internet service.
With over 10 million individual users and hundreds of thousands more enterprises, Optus is the country's second-largest provider.
The disruption has caused transit delays, shut down hospital phone lines, and brought payment systems to a halt.
The exact reason is unknown, although Optus claims there is no proof of a cyber assault.
As a result of a cyber assault, the corporation suffered what was thought to be the largest data breach in Australian history last year.
People throughout the country were unable to contact emergency services or vital hotline numbers as a result of the outage, which also momentarily halted rail services in the state of Victoria and certain hospital connections.
The outage was detected at about 04:00 (17:00 GMT) on Wednesday. In a seven-hour update, CEO Kelly Bayer Rosmarin stated that her team had not yet determined what went wrong.
"The teams are trying many different angles, and we will not rest until the service is back up for our customers," she stated, phoning onto local radio via WhatsApp.
Later, the company stated that it had begun to restore some of its services.
Other companies that use the Optus network were also affected, including Amaysim, Aussie Broadband, Moose Mobile, and others.
According to one Optus customer, the incident has prevented her from receiving critical information concerning her father's cancer treatment.
"I'm just waiting for results, and I can't even get those through," said Danielle Hopwood.
Annie, another client, told local radio that she learned about the outage when her cat's automated Wi-Fi-enabled feeder stopped.
Michelle Rowland, Australia's Communications Minister, said it was an anxious morning for many Australians and urged the corporation to be honest and "timely" in their customer updates.
"My understanding is that this is a fault deep in the core, so it is a fault that is quite fundamental to the network," she went on to say.
Bayer Rosmarin has apologized for the disruption and said the company will provide updates throughout the day.