How do I identify unknown charges linked to my Apple Account?

As always, you can see what your being charged for by viewing your Purchase History.

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

You can view and cancel subscriptions here:

View or cancel app subscriptions on iPhone - Apple Support

• If you do not see those purchases there, it may indicate that your card has been compromised by using it at a retail terminal that a scammer installed a skimmer/shimmer to read your card details. Contacting your bank would be the appropriate response for a card that has been compromised.
• If you are the Organizer of a family plan that uses Purchase Sharing, then members can make charges that are billed to your payment method and those charges will appear under their Apple ID.
• For purchases on your device, it requires double clicking the side button with the amount showing on the screen, followed by verification with e FaceID/Passcode. For a free trial, it will show the trial period along with the subscriptions price you will be charged if not cancelled at least 24 hours before the trial period ends.
• If you have given your Passcode to someone else, you have authorized them to use your device and that includes for purchases. You would need to set Screen Time restrictions to prevent that from happening if allowing anyone else access to your phone.