Review the information in this support article by clicking on the link to learn how to cancel a subscription from Apple. ➔ If you want to cancel a subscription from Apple - Apple Support
• "If you signed up [which involves very intentional steps by you or a user of your device, accompanied by warnings along the way] for a free or discounted trial subscription and you don't want to renew it, cancel it at least 24 hours before the trial ends."
If you didn't end the subscription in time you are responsible for paying for it. You can later ask for a refund if you wish.
If you wish to pursue a refund, follow the directions in this support article about how to request a refund for apps or content that you bought from Apple ➔ Request a refund for apps or content that you bought from Apple - Apple Support According to Apple’s terms, refunds are only made to remedy defective or unavailable product. You can request a refund on other grounds but those refunds are entirely discretionary and not guaranteed. Special terms also apply for some countries: About canceling subscriptions in Germany, Israel, South Africa, or Türkiye - Apple Support
You cannot ask for a refund until you have actually paid for the item, and once an item is billed you cannot cancel the purchase—you must pay for it or Apple will block your use of the store until you do.
If you do not have a payment method you can see if adding balance to your account with Apple by using a gift card will work. Read this support article to learn how to redeem your Apple Gift Card or App Store & iTunes gift card --> How to redeem your Apple Gift Card, App Store Card, or App Store & iTunes Gift Card - Apple Support