A Telstra spokesperson said: "We continue to investigate the issue affecting data services, including EFTPOS and access to ATMS, for a number of enterprise customers nationally".
They have advised customers that they can still use NetBank and the CommBank app as usual.
The banking institution also revealed to us which of its services are being impacted.
Caltex and Woolworths also reported issues with their payment systems. Our teams are communicating with external providers on when services will be restored & we'll keep you updated.
It's taken hours but telco giant Telstra has managed to put most bank and retail customers caught out at ATMs and checkouts back online after an outage. The outage then cascaded into a higher number of calls than usual into its call centre.
The New South Wales ambulance service said there have been no interruptions to emergency services while it works with Telstra to resolve technical issues.
Payments, ATMs and eftpos across Australia have been knocked offline by a Telstra outage.
The CBA experienced problems with some of its merchant payment terminals, leaving some retailers unable to accept card payments. If you or your business are experiencing issues, tell us about it in the comments.
Telstra apologised "for any issues caused" said it will provide an update once it knows more.
"Some services are returning to normal and we thank customers for their patience".
The spokesperson also said the cause of the problem is not internal but due to "one of [its] telecommunication providers".
"The cause of the problem is under urgent investigation".
Westpac said it was aware of some branches in Sydney being "non-operational due to a broader network failure in the region".
Westpac tweeted on Thursday night that the majority of the branches, ATMs and services impacted were "back up and running" before thanking customers for their patience. "Online banking is working normally", the red and white bank said.