There are reports of a major outage on Telstra's mobile services this afternoon.
Customers have taken to Twitter to vent their frustration - with Telstra's social media team confirming they are experiencing some issues.
The issue appears to impact users' ability to make and receive calls.
A Telstra spokesperson apologised for the inconvenience:
"We apologise for an issue impacting some 4G voice calls. Customers who are impacted can switch to 3G to make calls.
"Data and 3G services are not impacted. We are working to resolve the issue as soon as possible."