A family has spoken about the terrifying moment they feared for a loved one's life when they couldn't call for help during the Optus triple-zero outage.

The aftermath of the incident is continuing to unfold, with revelations of further Australians left unable to contact emergency services, and police deployed after the telco's admission more people were initially overlooked in assessments of the impact on triple zero calls.

One family recounted to 9News the fear experienced when they were unable to call for help as their loved one, Steven, collapsed, suffering a stroke.

The grandfather is lucky to be alive after repeated triple-zero calls failed.

"You can't help them, you're trying to contact someone who can help them and they're not responding," Doug Costello, Steven's son-in-la

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