If there are corrections to be made on the return and you need to unfile it from QuickBooks, I'd recommend contacting our Customer Care Support team again. They are the ones who can check your account with us and help you make amendments to an erroneous filing.
Here's how to contact our Live Support:
Go to Help at the top menu, then select Contact Us.
Enter your concern in the What can we help you with? field.
Click Let's talk.
Once done, select Start a chat or Get a callback option.
Here are some helpful articles to learn more about filing CIS in QuickBooks Online: