@Yakima You will have to contact Optus Billing to sort this out. The Optus staff that are part of the Yes Crowd do not have to customer accounts, and direct technical support tools. You can message them, reach out via social media Facebook, Instagram or Telephone. If you are telephoning it be better to call during business hours Monday to Friday.
Optus will generally transfer any money debited into your account and then use it for bills. You should now have a $40 credit in your Optus account that will be used to pay your bill next month (if you do nothing).
If you need it back before then then what tiger says is spot on.