Once you activate a free trial through iTunes, you will need to cancel before the end of the trial period to avoid being charged for the annual subscription.
Please note: Calm is not able to cancel a free trial on your behalf.
You can cancel through the iTunes account settings on your iPhone or iPad, or in desktop iTunes on a computer. Please see this support article from Apple for details on how to manage a subscription: http://support.apple.com/kb/ht4098
If you do not see Calm listed, you are using the free version of Calm and have not activated a subscription trial.
If you do see Calm - On the Calm subscription screen, tap the "Cancel Subscription" button.
If you do not see the "Cancel Subscription" button, this means it has already been cancelled. Once the free trial has been cancelled, you will no longer see a cancel button. Instead, you will see an "Expires [date]" listed in the subscription description in the Your Subscription section on that page, with renewal options below.
If you prefer, you can also access these subscription settings through the Calm app "Manage Subscription" page. Tap the More button on your home screen and then tap the gear icon in the upper left corner. In Settings, please tap "Manage Subscription" and on the page that appears, tap the word 'here' to be re-directed to your phone's Subscription settings.
If you have been charged for a subscription and no longer wish to use Calm, you can request a refund from Apple. Please note, you will need to work with Apple directly, as Calm is not able to manage in-app purchases or offer refunds on their behalf. You can contact iTunes Customer Support directly at https://getsupport.apple.com/.