Your hotline staff and IVR suggested otherwise. They keep asking me to do it via MyAccount, until I told them the error message.
If MyAccount is not working properly, why does it exist and Optus keeps promoting it?
Anyway, thanks for passing the feedback to MyAccount team. I will try it again and see if there is any improvement later. Hopefully you won't see me chasing you in here again.
We'd love to check out what might be causing this for you if you'd like to PM me with your account details (username/ phone number/ account number) as well as your full name and date of birth.