If you need to cancel a subscription for any app on the App Store (or check what subscriptions you have active on your account), you can do it in your iTunes account. See here for more details:
https://support.apple.com/en-us/HT202039
We recommend canceling your subscription at least 24 hours before your renewal date to make sure that you won't be charged for another term.
Please also note that deleting the app does not cancel your subscription.