There are three possibilities. If you’re the organizer of an Apple Family Sharing Group and Purchase Sharing is enabled, it’s another group member’s purpose.
The second possibility is a subscription was not canceled and this is the renewal charge.
The third possibility is your payment details (credit or debit card) is compromised.
You can resolve the first two by reviewing the information at the links below. The first link shows your purchases from Apple. You can also use the form provided to request a refund. If it’s a subscription, you’ll want to cancel the subscription too.
https://reportaproblem.apple.com/
If you want to cancel a subscription from Apple - Apple Support
If you iTunes charges are not at the link, the charge may still be pending at your bank. A request for refund cannot be made on a pending charge. If the charge is finalized and not shown, you’ll payment details are compromised and being used by fraudsters to make purchases using your compromised details.
Report the fraudulent charges to your bank using the phone number printed on the back of the card. Be sure and talk to the bank’s fraud department and not their regular support team.