Thanks,
So I ended up having to call our Telecom company and he told me something new that an extension can appear in another places. He proceeded to tell me about the category Multiline Appearance Groups that shows all the locations that an extension appears. So the extension was not deleting from the rerouting because it needed to be deleted from other devices/places first before I could put it on another controller, etc.
Thanks. Hope this is understandable.