Extra charge

Where did you see this charge? See—>If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement - Apple Support

You can also review your purchase history—>See your purchase history for the App Store or iTunes Store - Apple Support

Somebody has gained unauthorized access to you Apple ID

You can get assistance at the official support site

please go here for official support -> support.apple.com

Or the OP has a subscription they forgot about. Or it was in a scam email. While a hacked Apple ID is a possibility, it’s way down on the list.