Australians with dozens of types of Samsung mobile phones may not be able to have their triple-zero calls connected.

Telstra and Optus on Wednesday alerted customers to the issue with some older mobile devices calling triple zero in certain circumstances.

Testing identified 71 older Samsung mobile devices did not correctly connect to the Vodafone mobile network when Telstra and Optus service was unavailable.

Telstra notified Samsung and other telcos when it discovered the flaw.

"For the avoidance of doubt, this isn't an issue on our end and these devices still work perfectly fine on our network," a Telstra spokeswoman said.

The list of affected devices are Galaxy A7 (2017), Galaxy A5 2017, Galaxy J1 2016, Galaxy J3 2016, Galaxy J5 2017, Galaxy Note 5, Galaxy S6, Galaxy S6 edge, Galaxy

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