TELSTRA is still trying to identify the cause of a nationwide outage seven hours after it shut down voice and data services for millions of its customers.

Australia’s largest mobile carrier Telstra suffered its second nationwide mobile outage this month, with 4G services and internet connections cut off to customers around the country.

It also raised concerns about callers’ ability to contact Triple Zero.

The first reports of a widespread outage appeared just before 10am (AEST), with Telstra customers reporting they had been forced back to a 3G connection, and were no longer able to access the internet.

While the company did not initially acknowledge the problem, more than 3600 Telstra customers reported issues to Aussie Outages.

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The issue is impacting some 4G mobile voice and data services nationally, which is also causing congestion for 3G services. We're working to resolve the issue and are investigating the root cause. We're sorry for the inconvenience. — Telstra (@Telstra) May 21, 2018

A Telstra spokesman said most services were restored within five hours, though it had not identified the hardware or software fault at the root of the problem.

Ironically, the latest problem also downed Telstra’s Service Status page, where customers are asked to check whether there are planned outages or maintenance happening in their area.

The company’s social media team finally acknowledged the problems after 10.40am, replying to concerned customers that there was “an issue impacting our mobile network”.

NSW police said some people might have trouble contacting Triple Zero but in a statement Telstra said: calls to 000 will connect over others carriers’ networks where they have mobile coverage”.

Triple Zero calls are designed to go through even if your phone network is down. If they can’t get through on Telstra’s network, they automatically reroute to another carriers’ network.

NSW, South Australia and ACT residents were advised to call 131 444 if they are experiencing an emergency and are unable to get through to 000. Callers from Victoria have been advised to keep calling 000.

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We're aware of a national @Telstra outage and monitoring impacts on Vic's triple zero service. If you're unable to get through to triple zero from your mobile phone please find a landline phone and try again. Continue to call 000 for emergency help. — ESTA000 (@ESTA000) May 21, 2018

This outage may affect those attempting to call Triple Zero - 000 or Police Assistance Line - 131 444.



Until issue is resolved, police are advising those affected, where possible, to use a phone belonging to another carrier or a landline when attempting to call these numbers. https://t.co/9uiBfnY4ek — NSW Police (@nswpolice) May 21, 2018

Victoria’s train network was also affected.

12:10 Southern Cross - Waurn Ponds train will not run due to a Telstra outage. Customers are asked to travel per the 12:30 SCS to South Geelong. — V/Line Geelong Line (@vline_geelong) May 21, 2018

Hi Brendan. The train driver needs to radio the train controller before departure. The radio communicates via the Telstra network and therefore the driver was unable to complete a radio test which is a critical safety requirement. — V/Line Geelong Line (@vline_geelong) May 21, 2018

Four hours after the outage began, a Telstra spokesman said mobile phone services were being restored but the company was “still working to resolve intermittent issues or delayed call connection for some customers”.

Frustrated and angry customers flooded Telstra’s social media profiles with messages following the outage, including many demanding compensation for repeated problems on what the company advertises as “Australia’s best mobile network”.

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media_camera This Telstra outage map shows the affected areas. Picture: Supplied

One Facebook user wrote “every couple of weeks there is an issue now… compensate all the customers, I say,” while another suggested the company give its subscribers “one to two months free, especially since this seems to be an ongoing problem”.

In 2016, Telstra granted its users two “free data days” to download as much as they wanted from mobile services without charge following a series of nationwide outages.

The outage also comes after poor financial results from Telstra, as the company warned investors its earnings were shrinking in a tough, more competitive market despite attracting 60,000 more postpaid mobile customers in the third quarter of the year.

The telco also faces legal action from rival Optus, which has taken the company to court over its advertisements for an “unlimited” mobile phone plan.

“Without any qualification, these advertisements are likely to mislead customers,” Optus claimed in court documents.

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media_camera Today’s issue has also affected Telstra’s Service Status page. Picture: Supplied

The nationwide outage comes just 20 days after the last widespread issue, that downed mobile phone connection for two hours.

A Telstra spokesman later confirmed the problems were caused “by technical changes made ahead of upgrades to mobile traffic control equipment in Telstra’s Exhibition Street exchange in Melbourne”.

Telstra’s network also failed on May 4 in an outage that affected some Triple-Zero calls for 10 hours across five states and is currently the subject of a formal investigation by the Federal Government.

The issue has affected major metropolitan centres including Sydney, Melbourne, Brisbane and Adelaide and regional areas including North Queensland.

Just got a voicemail (without my phone ringing) from what sounded like a computer talking in Chinese or Japanese. Now my phone has lost all service. Should I be concerned? — Scott Bailey (@ScottBaileyAAP) May 21, 2018

‘IT’S HAPPENED AGAIN’

On May 1, Telstra suffered an embarrassing two-hour, nationwide outage on the same day it launched its biggest mobile phone plan change in years.

The company’s 4G mobile network stopped connecting phone calls around 1pm, with customers in all state capitals unable to make or receive calls over the network, in an outage that saw many frustrated customers turn to social media with complaints.

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Ironically, Telstra’s outage also initially affected its service status page that could have alerted users to the problem.

A Telstra spokesman said the outage was resolved after 3pm, with services progressively turned back on for customers.

media_camera Telstra’s outage issues have become a common theme. Picture: Getty

The 4G network problem arrived at a particularly inopportune time for Telstra, which had announced a generous new $69 monthly mobile phone plan, featuring unlimited phone calls and text messages, and 40 gigabytes of 4G data downloads.

The company will go head-to-head with Vodafone, which launched three competing mobile phone plans between $60 and $100 per month.

Telstra previously suffered a string of seven network outages in 2016, including a six-hour outage that followed chief executive Andy Penn’s announcement of a $250 million investment to improve infrastructure and prevent downtime.