Building site contractors severed a 1200-pair cable on the NSW South Coast before concreting over it a fortnight ago, knocking out about 800 residential and business lines on Telstra's network.
The break happened on the site of a new Woolworths supermarket in the town of Ulladulla, according to a report by the Milton-Ulladulla Times.
It caused four days of work for Telstra crews, with the replacement job requiring ducting to be brought down from Sydney.
"A third party contractor working in the area severed the cable – fortunately not a major one," Telstra's area general manager for the Illawarra region Michael Marom told iTnews.
"Inadvertently, or perhaps because they weren't aware they'd cut the cable, they concreted over the top of it.
"By the time we'd located the fault in the area and got to the scene, we had to organise another contractor to break the concrete because it had set. [Our] crews were there for four days".
Marom lamented that the break was entirely avoidable.
"A simple phone call [to Dial Before You Dig] would have avoided four days of work and the issues."
Marom said that most issues with cable breaks in the Illawarra were weather-related, such as storms or water damage, rather than being from excavation work.