How do I stop unauthorized charges on my Apple Account?

Purchases on your device require double clicking the side button with the amount showing on the screen, followed by verification with FaceID/TouchID or Passcode. Anyone that has your Passcode is authorized to make purchases on your device.

• What did you determine the purchase was for:

View your purchase history for the App Store and other Apple media services - Apple Support

• Have you reviewed your subscriptions:

View or cancel app subscriptions on iPhone - Apple Support

If you started a free trial previously and did not cancel at least 24 hours before the trail period ends, it will become a subscription. That is detailed on the same authorization screen that required your Passcode.

I would also suggest to review if there are other devices that are signed into your account by going to Settings > [name on top], and scroll to the bottom to view those devices. There may be additional steps you need to take to secure your account or your payment method, but without the additional details on the charges, we cannot guess how they occurred in the first place.

Take a look at Billed, but you didn’t buy? - Apple Community