Select the Account menu and choose Account Profile.
Scroll down and click the Close Account button.
Follow the on-screen instructions to successfully turn off the merchant services.
I've added some screenshots for your additional reference.
Once done, QuickBooks will send you an email within one business day that confirms your QuickBooks Payment account is closed. To know more about the availability of the data after you close your QuickBooks payments account, you can check out this article: Cancel your QuickBooks Payments subscription.