Q: cancel itunes subscription

There are instructions for stopping the auto-renewal on this page : http://support.apple.com/kb/HT4914

If you want to cancel it during its current subscription period then you will need to try contacting iTunes support : http://www.apple.com/support/itunes/contact/- click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption