Most Optus and Vodafone customers should again be able to make phone calls, send texts and use data after both major providers suffered widespread network outages.
Vodafone's problems began in Western Australia on Thursday morning before spreading nationwide.
The state was still experiencing problems by late afternoon when services had been restored elsewhere.
"All voice and SMS services are now restored nationally with the exception of Western Australia," a spokeswoman told AAP late on Thursday.
"Our engineers are working fast to ensure all services are fully restored."
Optus has advised its customers via Twitter that those affected should turn their phone off and on.
"This should fix the problem," the provider posted. "We apologise again for the inconvenience."
The outages sparked a flurry of posts on social media as customers spoke about their frustrations.