Based on my understanding of your scenario, you need to refresh the list of customers only when you save them on the edit
CustomerEditView, by passing ResetView parameter.
Please take into account, is not possible to clear the NavigationContext
Parameters´s property since is read-only.
In case you need to go back without sending the refresh parameter, you could navigate to the
CustomerView by simply retrieving the RegionManager and navigate again to the view.
var regionManager = ServiceLocator.Current.GetInstance<IRegionManager>();
In the other hand, regarding NavigationService.GoBack() method, as documentation shows “Navigates to the most recent entry in back navigation history, if there is one”. That says, your first view is going to be loaded
exactly the same way when you start the navigation process.
You can read more about Navigation, in Prism documentation
Chapter 8: Navigation.
I hope you find this information useful.