Hi topiarymadness-o,
To unlodge a BAS you can contact an accountant user or support team for further assistance.
You can find the contact details here: https://help.quickbooks.intuit.com/en_AU/contact.
For your reference, you can also check on this article: Unlodging a BAS as an Accountant User.
Thank you and please let us know if you require any additional assistance. Have a nice day.