Good news - it's super easy to modify your subscription! Just follow these steps:
Go to Settings > [your name] > iTunes & App Store.
Tap your Apple ID at the top of the screen.
Tap View Apple ID. You might need to authenticate your Apple ID.
Tap the subscription that you want to manage.If you're being charged for a subscription, but you don't see it in your list of subscriptions, it might be billed through someone other than Apple. Learn what to do if you still can’t view your subscription.
Use the options to manage your subscription. You can choose a different subscription offering, or tap Cancel Subscription to cancel your subscription. If you cancel, your subscription will stop at the end of the current billing cycle.
Still need help? Here is an article with more information: