"These things happen", said one man on Facebook, coming to the bank's defence. "We apologise to all of our customers who are inconvenienced by this", a CBA spokesman said.
A spokesperson for Telstra said it was investigating the issue.
"We continue to investigate the issue affecting data services", a Telstra spokesman said.
By 6pm, Telstra said it had the problem in hand and that services were starting to return.
Commonwealth Bank customers first reported issues earlier this afternoon with ATMs and EFPTOS. There are also issues for customers logging on to its CommSec site. She added that the bank's call-centre is experiencing a "higher than normal" call volume and said there is no need for retail or business customers to call the bank.
"We're sorry for any issues caused and will provide an update when we know more".
"The cause of the problem is under urgent investigation and we are working to have full services restored as a matter of priority".
A Telstra network outage has thrown the nation into chaos, with Commonwealth, ANZ and Westpac banks, plus Woolworths and Australia Post experiencing issues across the country.
- CommBank (@CommBank) July 11, 2019We're aware some branches, ATMs & services in Sydney metro are non-operational due to a broader network failure in the region. "Online banking is working normally", the red and white bank said. Service station chain Caltex has also confirmed an impact from the outage, meaning customers are being unable to pay for some purchases.
Australia Post has also confirmed that Eftpos and other banking services are now disrupted, blaming a "supplier issue".
The problem has hit as Australian cities head into to busy peak hour commuter rush with most capitals also having Thursday late night trading. "Rest assured we are urgently looking into this and will have further updates soon", the company wrote on Twitter.
Some people have also taken to Twitter claiming they can't get in touch with the bank on the phone, after being left on hold for ages with other calls going straight to a recorded message. Error code TCP/IP failure. I've already tried calling and been on hold for over 30 minutes.