If you subscribed or started a free trial via the App Store, refund requests are handled directly by Apple. You can submit a request following the instructions:
- Visit reportaproblem.apple.com.
- Sign in using your Apple ID and password.
- Choose "Request a refund" from the drop-down list.
- Specify the reason for your refund request and tap "Next."
- Pick the relevant service you purchased and proceed by tapping "Submit."
For more detailed instructions, please visit https://support.apple.com/en-en/HT204084.