The only possibility is to deactivate: be logged in, go to http://www.prize.com/account/edit and click deactivate.
If you’ve been paying, also read this to withdraw before you cancel: http://support.prize.com/knowledgebase/articles/37579-cancelling-your-account
Alternatively you could try and request full deletion using http://support.prize.com/knowledgebase/ and then, use the webform on your right hand: ‘Contact Support’.
URLS:
http://www.prize.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.