Received email for a a charge I didn’t make

If you received an email, a message, or a calendar notification about an unfamiliar purchase or subscription, it’s likely a phishing scam and nothing was actually charged to your account. Don't ever call, email or click on any links in that message. Just delete it and you should be fine.

If you want to confirm if the purchase was really made, log into your Apple ID/iTunes account directly and check your billing or purchase history. If there is an unauthorized purchase shown there, you can file for a refund from there using the Report a Problem form: 

https://reportaproblem.apple.com/

Recognize and avoid phishing messages, phony support calls, and other scams (Apple article):

https://support.apple.com/en-us/HT204759

I'm not sure how you expect Apple to prevent this from happening.

It's an endemic problem with email - anyone can (rightly or wrongly) send an email saying just about anything. It doesn't come from Apple, doesn't touch their servers, and they don't control the content, so what is it you expect them to do?

Think of it another way - anyone can send an email saying they are your country's president/king/prime minister/whatever and calling on you to serve your country; or your bank manager saying you're overdrawn and owe money; or a Nigerian prince saying he has a foolproof get-rich-quick deal for you. It's entirely on you if you respond to that email without considering the authenticity of the email.

It's this lack of authentication and authenticity in email that allows spam to continue to propagate.

It's not limited to email though - the same thing has happened for years with snail mail. The difference is it costs to send a message via mail and so email has become the preferred medium where millions of such messages can be sent for almost no cost.