I still got charged for a free trial subscription that I had cancelled before billing day (the end of trial period)

Request a refund for apps or content that you bought from Apple

Some purchases from the App Store, iTunes Store, Apple Books, or other Apple services might be eligible for a refund. You can use any device with a web browser to request a refund.

How to request a refund

1. Sign in to reportaproblem.apple.com.
2. Tap or click "I'd like to," then choose "Request a refund."
3. 
   
4. 
5. Choose the reason why you want a refund, then choose Next.
6. 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.

Wait 24 to 48 hours for an update on your request

If your request is approved by Apple, it might take additional time for the funds to return to your payment method. Learn how to check the status of your refund request.

If you can't find the charge on reportaproblem.apple.com

Find out if another account was used to make a purchase.

1. Search your email for the words "receipt from Apple" or "invoice from Apple".
2. Look for a receipt that matches the amount that you want to request a refund for.
3. On the receipt, see what was purchased and which Apple ID was used.
4. 
   
5. 

Once you've found the receipt, try these steps:

• If the receipt is for a member of your Family Sharing group and you're the family organizer, you can still request a refund on reportaproblem.apple.com. Tap or click the Apple ID button, then choose All. Purchases charged to your shared payment method appear.
• If the receipt is for a different Apple ID, use that Apple ID to sign in to reportaproblem.apple.com.

If you can't find a receipt, try these steps:

• If the charge is pending, you canʼt request a refund yet. After you receive an email receipt, try to request a refund again.
• If you have an unpaid order, you need to pay for that order before you request a refund. You might need to update your payment information.
• In the European Union, purchases for digital goods and services might not be made through Apple. Learn more about purchases not billed through the App Store or the App Store's In-App Purchase system.
• If you have multiple Apple IDs, use each one to sign in to reportaproblem.apple.com and look for the charge you want to request a refund for.

Start here:

Request a refund for apps or content that you bought from Apple - Apple Support

it didn’t work :(