Virgin Mobile has announced that services are back up after a brief outage on Thursday morning, although users may have to restart their phones in order to make calls.
The telecommunications provider, which wholesales Optus' 4G network, said the issue only affected some of its customers, with those users to be credited their access fee for the day in reparation.
"The network issue experienced by some of customers this morning is now resolved, but customers may have to turn their phone off and on again to access the network," Virgin said in a statement.
"We sincerely apologise for the loss of service; we know how important it is to be connected. We will be thoroughly investigating the issue, and will be crediting all affected customers their access fee for the day today."
Virgin's outage comes a day after TPG-owned telecommunications provider iiNet experienced a nationwide outage across its voice, email, and contact centre services due to a "serious fault".
iiNet customers on Wednesday experienced difficulties in reaching contact centres, as well as with using email and voice services.
TPG has since restored services.
Incumbent telco Telstra was forced to undergo a comprehensive network services review after itself experiencing three outages at the beginning of this year.
Telstra customers were subjected to three outages over a period of six weeks: The first on February 22, which affected prepaid and post-paid mobile services and was caused by "embarrassing human error"; the second on March 17, which involved an hours-long national mobile data and voice outage; and the third on March 22, which was a smaller voice outage.
Telstra has since committed to spending an additional AU$50 million to improving the monitoring and recovery times of its network. Of this AU$50 million, AU$25 million will be spent on installing monitoring equipment and tools for improved real-time traffic monitoring, while the other half will go towards improving network recovery time.