A Vodafone customer was repeatedly unable to ring triple-0 and says the major telco failed to help her fix the problem with her mobile phone for months.

She is amongst tens of thousands of customers using older Samsung devices who have been given 28 days to buy a new device or urgently update software to ensure they can call emergency services, before their phones are blocked from using their telco's mobile network.

Telstra revealed yesterday that testing found 71 Samsung devices were unable to reach triple-0 on the Vodafone network, when the Telstra or Optus networks were unavailable.

Telstra said the issue affected 11 older model Samsung Galaxy phones, which users would need to replace with newer devices, and about 60 models that required system updates.

Some Samsung phones unable to

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