Using the copy/super copy, you have to assign a new extension for the new device and then remove the old device before you can change it to the extension you need to remove. Note that you will still want to check the settings as many of them don't copy over using either copy or super copy. We quit using that feature because we had to make almost as many changes to the device after copying it as we did when we just used a template and then added the unique settings for that user.
