Communications, Electrical and Plumbing Union of Australia national president Shane Murphy said the sacking announcement had been made on Thursday.
The outage affected ATMs, Cabcharge services and EFTPOS services around the country.
“This Telstra outage has inconvenienced many thousands of people right across the country,” Murphy said.
“Telstra’s decision to axe 360 technical field employee jobs is about as short-sighted as it gets. These are the people that spring into action when there are issues like this one.
“Who is going to fix the system if you cut the jobs of everyone capable of doing it?
“This is another classic example of Telstra prioritising cost cutting ahead of its customers and its workforce.
“This once iconic telco is being driven into the ground, and customers and the workforce are being forced to bear the brunt of it.”