There's an option in your settings that lets QuickBooks automatically apply open credits to open invoices. We can turn that off to stop the auto-payment. We can do the same thing for bill payments, as well. I'll walk you through the steps.
Click on the Gear icon and choose Accounts and settings.
Go to Advanced and click the Automation section.
Turn off Automatically apply credits and Automatically apply bill payments. You can click the encircled question marks to see more details.
Click Save and click Done.
If you have other questions, you can always go back to this thread. Have a good one!