Telco TPG has been fined $400,000 for failing to provide access to emergency numbers for all customers.
A day after his TPG phone account was suspended, retired NSW police officer Michael Merrin fell seriously ill.
His wife tried to call triple-zero from their home line, but with all outgoing calls barred she had to use a mobile phone with patchy reception to get help.
It took 27 minutes for an ambulance to arrive, during which time Mr Merrin suffered a heart attack. He died in hospital days later.
The September 2011 case was just one of 193 occasions in which TPG customers were blocked from reaching emergency services.
Almost 6000 TPG customers with suspended or inactive accounts due to bills being unpaid or other reasons were denied access to emergency lines between March and September 2011.
The telco was fined $400,000 in the Federal Court on Wednesday, with Justice Mordecai Bromberg criticising the company's lax approach to important regulations.
"TPG's failure could easily have led to the death of a person who might otherwise have been saved," he said.
A software upgrade at TPG in 2011 barred all outgoing calls, including to emergency numbers, made from suspended and inactive accounts.
The Merrins' case alerted the company to the error, but not before 100 customers had tried to make emergency calls.
Justice Bromberg said while the error may have been inadvertent, TPG had not taken reasonable steps to avoid it happening.
The Australian Communications and Media Authority (ACMA), who brought the action against TPG, said telcos were on notice about their legal responsibilities.
"The obligation to give triple-zero access is of paramount importance," ACMA chairman Chris Chapman said.
"All Australians need to be assured that any call they make to the triple-zero emergency call service will be connected."