At least 127 calls were unable to be transferred, including a call from the family of a Melbourne man who suffered a cardiac arrest on March 1.

Telstra has been fined $3m for a triple-0 outage earlier this year which led to 127 calls not being transferred to emergency services.

An investigation found the telecommunications company made 473 breaches during a disruption in March, with Telstra's Triple Zero call centre failing to properly transfer calls to emergency services.

Telstra has been fined $3 million for a Triple Zero outage earlier this year that led to 127 calls not being transferred to emergency services. The incident, on March 1, was previously attributed to a confluence of factors, including a database failure and a software bug.