You cannot change url of hubs. This is the link to the Learning Center hub on this topic - http://hubpages.com/learningcenter/title-category-... It is not necessary that url should be the same as a hub title. So, even if you change hub title, you can leave url intact as long as it is relevant and search engine-friendly. If you really want to change url, you have to unpublish the hub and start all over again.