If the charge shows apple.com/bill or something similar, check your Apple purchase history first:
https://reportaproblem.apple.com
Sign in with your Apple Account and you can search for the exact amount that was deducted. Apple may also combine several purchases or subscriptions into one charge.
If you don’t recognize anything there, also check whether another family member’s purchases are being billed to your payment method. If the charge still can’t be identified, contact Apple Support or your bank before disputing it.