A statement from Vodafone on Friday evening said the underlying network issue had been resolved but that customers had to be reconnected to 4G progressively "so the 4G network doesn't become overloaded".

"We hope to complete this re-connection process over the next few hours," a spokesperson said.

"Until this process is completed, customers' experience will continue to be impacted. We understand this has been frustrating and inconvenient for many customers and we are truly sorry."

Vodafone mobile customers started noticing problems from around 10.30am on Friday, causing chaos for many as they went about work and travel.

"Literally on the phone to my partner giving him directions to get to his jobs because he can't access maps," tweeted one person.

Earlier on Friday, Vodafone advised customers that they would experience difficulties making calls and would experience slower data speeds.

"Data services may be falling back to 3G intermittently, causing congestion and slower speeds," Vodafone tweeted.

Vodafone told AAP that if customers are using NBN for wi-fi, those services are not affected by the outage.

Australian Associated Press