For unfamiliar charges work your way through the steps in this article: "If you see ‘itunes.com/bill‘ or an unfamiliar charge on your bank, credit card, or debit statement" - https://support.apple.com/HT201382
Prime suspects for unusual charges are subscriptions and purchases made by family members under Family Sharing (if applicable). These will not show in your purchase history but may appear on your payment card. Your email receipt will show the purchaser's Apple ID but details will have to be viewed from the purchaser's account.
"If the subscription that you want to cancel is not listed", click here --> https://support.apple.com/HT212052
If you still can't find a subscription, contact Apple Support using the link at the end of the support article.
If neither you nor a family member (if applicable) has a record of this purchase and you only saw it on a statement for a card you alone control, contact your bank or card company about card fraud. Apple does not handle that.