In order to resolve the issue that you are describing, it may be best to speak to our Support team so they can assist.
Can you please reach out to us on 1800 046 038, and one of our representatives can help you with your BAS issue.
Our phone lines are available from 8:30am-6:30pm AEST.
Are you referring to unlodging a BAS in QuickBooks Online? Our support team aren't able to access your file and delete records on your behalf, however unlodging a BAS can be done with you as part of troubleshooting. If they have completed this with you, you can easily recreate this by clicking on the 'Prepare BAS' section of your GST centre and following the prompts to mark as lodged once more. If you have undone a payment recorded against a BAS, you can also recreate this (see here for full steps).
Alternatively you are more than welcome to reach out to the support team once more to determine exactly what troubleshooting has been performed and what steps to now take to achieve your goal. They can get eyes on your account with you to provide the best assistance possible.