Contact support prior to the date of the renewal to cancel your subscription, if that's your intention.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
If you wish to renew with a retail product key or PIN, you can do that at any time and it extends the subscription for 12 months from the original expiration date.
-steve