If you want to unsubscribe, according to the Private Policy of Apple, developers are not allowed to access to your subscription management. So you need to do unsubscription by yourself.

To cancel your subscription, simply follow the instructions below:

• Open the Settings app on your phone.
• Tap your name.
• Tap Subscriptions.
• Tap the subscription that you want to manage.
• Tap Cancel Subscription (Or if you want to cancel Apple One but keep some subscriptions, tap Choose Individual Services.) If you don’t see Cancel, the subscription is already canceled and won't renew.

Also you can follow the link: https://support.apple.com/en-us/HT202039

How to request a refund:

• Sign in to reportaproblem.apple.com.
• Tap or click "I'd like to," then choose "Request a refund."
• Choose the reason why you want a refund, then choose Next.
• Choose the app, subscription, or other item, then choose Submit. If you were charged for a subscription that you no longer want, you can also cancel the subscription.

Also you can follow the link: https://support.apple.com/en-us/HT204084