Here you can change any part of the service.

Note, that this will not update the calendar item that created it.

The codes that are available on this screen are based on the Staff (user) that is selected for the service. If you do not see a code showing in the dropdown, that means the user did not have the permission to select that code when creating the calendar item. If you want to use a code that is not in the dropdown, you will need to add the code to a group or department that the user is a member of. This is done under User Maintenance > (Groups or Departments)