Unless this is a scam you are seeing in an email or a message and there isn’t actually any purchase, purchases are indeed “authorized” by somebody with access to your accounts, or equipment, or with your permission.
Your first step is to try to identify the reason for, and source of, any charges. They may be perfectly valid charges you simply do not recognize. In the case of emails or messages there is the possibility they are not real at all (phishing attempts).
The support article If you see 'apple.com/bill' on your billing statement - Apple Support and the related article Get help with charges from apple.com/bill - Apple Support explain how you can check your iTunes and App Stores purchase history, cancel subscriptions (remember that these need to be canceled at least 24 hours in advance), and track possible sources of unrecognized Apple charges you may see on a bill. These may be purchases by Family Sharing members, others sharing your card (such as a spouse or partner, or a second Apple Account you have; you may not see a receipt).
The article also provides a specific link for contacting Apple if you cannot trace the source of charges, e.g., if you subscribed to something directly with a third party, see: About purchases not billed through the App Store or Apple In-App Purchase - Apple Support instead. In that case you need to work directly with the vendor, not Apple. See also: Fabulous SAS - Unethical app, please dele… - Apple Community
If you use Apple Card you may find this document helpful too ➞ If you see an Apple Services charge you don't recognize on your Apple Card - Apple Support
Also note this service: View your App Store and iTunes Store purchases directly from your financial institution - Apple Support
"When you sign in to your financial institution website or mobile app and view your recent purchases from the App Store, iTunes Store, Apple Books, or for Apple Music or iCloud services, you may see an option—such as View Receipt—that allows you to view more details about your transaction."
If using Family Sharing and viewing purchase history under Report A Problem, make sure the “Apple ID” box is set to “All.” If a purchase is listed in your purchase history and you want to ask for a refund, read this article about how to request a refund for apps or content that you bought from Apple ➞ https://support.apple.com/HT204084 Remember that many apps have trial periods with subscriptions that then start automatically unless you cancel them in time. If a Family Sharing member made the purchase then you need to discuss this with that person. They would have to initiate any refund request.
If a reporting a problem request is unsuccessful or you have another issue you can also see if you can speak or chat with Apple. Click here ➞ https://support.apple.com/HT201232 Go to the bottom of the window and you may see options for a telephone call or chat session. This is not available in all countries and the phone numbers tend to not be international.