-You can cancel the free-trial subscription before the end of the free trial period by going to your Account Settings at iTunes Store.
-Any unused portion of a free trial period, if offered, will be forfeited when the user purchases a subscription to that publication, where applicable.
The free-trial subscription begins immediately but it won’t be billed until the free trial period is over.
Your subscription will automatically renew at the end of each term and your credit card will be charged through your iTunes account.
-Auto-renew can be turned off at any time from your iTunes account settings but refunds will not be provided for the unused portion of the term.