How to cancel Xbox LIVE Membership:
1) Log-in to your xbox.com account
2) On the top right hand side will have a drop box saying “My Xbox” click onto this dropbox and click on “My Account”
3) Click on the tab “Membership Level”
4) Next to “Automatic Renewal” click the “on” link
5) It will proompt you to turn it off by scrolling down and clicking next a few times to skip some attempts to get you to stay
6) You’re done