Yes, you can always deactivate the Customer and Credit Management plugin from the “Purchase Subscription” screen.
You can approach this screen either from the Plugins Screen or from the Manage Account Section. If you are coming from the Plugins screen, you need to click the Deactivate button on the plugin tile labelled Customer and Credit Management. If you are coming from the Manage Account section, navigate to the Already Active section on the Purchase Subscription screen. Remove the tick from the activation checkbox to mark the plugin as Inactive.
Upon deactivation, all the features and functionality added to the application are removed. Even though you deactivate, the plugin will remain “active” till the end of your current subscription cycle. However, you can always choose to reactivate the Plugin without incurring any additional charges during its subscription cycle.