Did you cancel at least 24 hours in advance? If not then you may have canceled too late.
Click on this link to review the information in the support article about canceling subscriptions ➔ https://support.apple.com/118428
Notes:
• “If you signed up 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." By using an app like this you are automatically agreeing (always read the fine print) to this happening, are responsible for reading if this will happen, and canceling the subscription before the trial ends. E.g., https://discussions.apple.com/thread/256230049?answerId=261793271022 Exceptions apply in some countries ➔ https://support.apple.com/108098
• Deleting an app does not cancel a subscription.
• Canceling a subscription does not automatically start a refund.
• This thread (particularly posts by Mac Jim ID) outlines complex scenarios regarding subscriptions and trials. ➔ https://discussions.apple.com/thread/256149847
If you still think you were unfairly charged then contact Apple and get a real person to whom you can present your evidence and ask for a final review:
This support page has information about contacting Apple support and service ➔ https://support.apple.com/106932 If live support options (chat and/or telephone) are available they will show near the bottom left.
- Telephone numbers may only work when calling from the same country.
- Chat options (telephone numbers appear as active links, not plain text) may depend upon cellular connectivity. If a number shows as an active link, click on it to see additional options.
- If chat is not available on the top level support page, try selecting your hardware and narrow down your issue to see if a support article offers a support link offering chat. For example, the contact support link on this page https://support.apple.com/119902#zerobalance offers a chat link about emptying account balance even on a computer where the top level page does not offer any chat.
With an iPhone, iPad, or Vision, you may be able to chat using the Apple Support App if it is available in your country —> https://apps.apple.com/app/apple-support/id1130498044