Unauthorized purchase

If you see 'itunes.com/bill' or an unfamiliar charge on your statement

Only Apple will be able to remove an unauthorized purchase. Remember that all transactions are considered final once the Purchase button is clicked.

The particular context here is unclear.

Lots and lots of fake purchase notifications are being received by folks:

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

If the unauthorized purchaser somehow has your Apple ID and password, you have bigger issues than the purchase.