A software change caused an issue for customers making mobile calls and was fixed about 2.30pm AEDT, a Telstra spokesperson said.

"There was no impact to data or 000 calls," the spokesperson said.

"The issue was caused by a software change and was fixed by rolling that back.

"We're sorry for the impact on people's days."

More than 2000 people had reported problems with Telstra to Downdetector from 1pm.

The telco confirmed the issue shortly before 2pm AEDT on social media.

A Telstra spokesperson earlier said testing had shown there was no impact on emergency calls to Triple 000.

"Mobile data is not impacted so if you're having trouble making calls, you can use services like Apple FaceTime, WhatsApp, Facebook Messenger and other data-based services to stay in touch while we get this issue sorted out," the spokesperson said.

"We're working on a fix and hope to get everything back up and running soon. We'll keep you updated."

The telco had an outage in May 2023 which blocked some customers from making or receiving calls.