Deleting a local user account does not delete the account from the address book and Device Quotas.
Try one or more of the following:
From the Embedded Web Server, click Address Book.
Select one or more users that you want to delete.
Click Delete.
From the Embedded Web Server, navigate to the configuration page for the application:
Apps > Device Quotas > Configure
From the User Accounts section, select the user that you want to delete.
Click Delete.
Click Apply.
If you still cannot resolve the problem, then contact your solution provider.