Hi Joseph,
If you feel that the content of your site has changed enough that it might be better suited in another category then you can use the "update listing" link. This link can be used for:
However it may be unlikely that a request for a listing in a top level category would be approved. The "update listing" link is just a suggestion, at the end of the day it is down to the editors to decide where the site is best suited in the directory based on the content. Sites are listed according to the content not where the sites competitors are listed.