Be logged in. Right top, hold your mouse pointer over your username (number). Click Account Settings. At the bottom of the page there is a link: Cancel Account. Use it. Another good part: all info of/about you will be erased. Well done Social Number.
URLS:
http://www.socialnumber.com/
http://socialnumber.com/user/
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.