If you select the Bills tab > Payment options > is nothing in that area? They keep changing the bloody thing and there was an issue with account numbers starting with 62 written up on the first link below. If that doesn't work Billing via the live chat on the second link below might be the go.
I contacted Optus and apparently one can't do that online. There are only two ways to update your credit card details including expiry date.
1. Ring them on 133 937 to change via a phone call
2. They can send by email (or maybe you can download) an updating form for you to complete and return.
Either way is pretty primitive compared to other organisations.
Yes I agree. I must say I have used many account portals in my life time and the Optus portal is by the worst in every possible way. I’m glad you got the matter sorted and thanks for the info on the 2 methods available.