A network outage has left Optus customers in a number of states unable to make or receive phone calls.
Optus users in Sydney, Melbourne, Brisbane and Adelaide have reported issues with making or receiving calls from other networks, while non-Optus customers are having trouble calling into the network.
Optus say they are aware of the outage and are working to resolve the problem.
UPDATE: Optus services are now restored.
An Optus spokesperson has said Optus customers may have experienced intermittent disruptions to voice services this morning as a result of a technical hardware failure. Mobile data services were fully operational and were not affected.
Optus can confirm services were restored at 9:20am AEST and apologise to customers who experienced any inconvenience and thank them for their patience.