Have you verified what the subscription was for here:
View or cancel app subscriptions on iPhone - Apple Support
And in your Purchase History here:
View your purchase history for the App Store and other Apple media services - Apple Support
You can request refunds for purchases managed by Apple. In most cases all transactions in the App Store are final, but at times Apple will consider a compassionate refund. It should never be expected though.
Request a refund for apps or content that you bought from Apple - Apple Support
The description does not identify what the charge is for. Subscribing to a subscription managed by Apple does require the user to double click the side button on the device with the terms of the free trial/subscription on the screen, followed by verification with FaceID/Touch ID or Passcode. If you signed up for a free trial, it does become a subscription and you will be charged if not cancelled a day before the subscription start date as seen on the Authorizations screen requiring your to double click. If you are the Organizer of a Family Plan using Purchase Sharing, you have authorized members to make purchases on your account.
Finding out how this happened is the key, and if you did not do it, then that means either your Apple Account has been compromised or your financial account has been compromised and the resolution will be much different.