Did you cancel at least 24 hours in advance?
This support article explains the details about canceling a subscription from Apple ➔ If you want to cancel a subscription from Apple - Apple Support
Note where it says if you don’t cancel trials more than 24 hours before your renewal date, your [trial] subscription might renew (as a regular paid subscription).
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 This support article explains how to check the status of a refund for apps or media content that you bought from Apple, and how long it takes to receive a refund if you are granted one --> Check the status of a refund for apps or content that you bought from Apple - Apple Support
* Legal - Apple Media Services - Apple section B