A purchase has been made that was not made by me

Scam, most likely.

Verify your purchases directly with Apple.

Some of the scams:

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

Goal of the scammers is to panic you, to scare you, to titillate you, to pique your interest, anything to get you to click on the link and log in to the scammers’ “Apple web portal login”, and expose your Apple ID and password.

More info:

See your purchase history for the App Store or iTunes Store - Apple Support

Identify legitimate emails from the App Store or iTunes Store - Apple Support

View, change, or cancel your subscriptions - Apple Support

...Though if you clicked on logged into the scammer’s links, change your Apple ID password yesterday.

If the only indication of the charges is from an email or text, be aware that it may be a phishing attempt to get you to log in to a site that appears to be Apple and divulge your password or credit card information. See: Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

and Identify legitimate emails from the App Store or iTunes Store - Apple Support

If it is a real charge, see the following instructions. They include information on contacting Apple Support if the other steps don't help: If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement - Apple Support