The telco is investigating an issue impacting its mobile network, with customers complaining about outages to calls and data. 

We’re working to fix an issue impacting some mobile services. Sorry for the inconvenience.

— Telstra (@Telstra) May 21, 2018

Issues to the 3G and 4G network could also be impacting calls to Triple Zero or the Police Assistance Line.

Police have advised those affected to use a phone with another carrier or a landline to call emergency services.

Outages across the Telstra 3G & 4G network may impact people trying to call Triple Zero (000) or the Police Assistance Line (131 444). Until resolved, if you need assistance use a phone with another carrier or a landline. Only call Triple Zero (000) if you have an emergency.

— NSW Police (@nswpolice) May 21, 2018

Telstra has since said 000 calls will connect via other carriers’ networks.

The telco has issued Macquarie Media the following statement:

We are working to resolve an issue impacting some 4G mobile voice and data services nationally which is also causing congestion for 3G services.

We apologise for the inconvenience and are working to resolve the issue as soon as possible.

We are still investigating the root cause. Calls to 000 will connect over other carriers’ networks where they have mobile coverage.