You cannot seem to delete your account.
However, you can contact them easily: http://www.smartphowned.com/about – ask them to do it manually for you. Make sure to include your account details in the message body.
URLS:
http://smartphoned.com
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.