Unauthorized Changes to My Billing Information

All emails such as that are scams attempting to scare you into calling a number or follow a link in the email to get your personal information. As long as you did not do that, all you need to do is delete the email.

At anytime, you can view your Purchase History here:

View your purchase history for the App Store and other Apple media services - Apple Support

To review your account billing information:

If you need to change or update your Apple Account payment method - Apple Support

For security, make sure you are using Two Factor Authentication:

Two-factor authentication for Apple Account - Apple Support

To help in identifying any future scams, review the Support Article here:

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

If you gave them your AppleID/Password, then you will immediately want to change the Password to your account and review the Support Article for when your account has been compromised:

Change your Apple Account password - Apple Support

If you think your Apple Account has been compromised - Apple Support

If you disclosed any financial account information, then you will want to contact your bank to secure your account.

Simply clicking a link in the email is not likely to do any harm unless you provided the personal information after clicking the link. Many times those links will direct you to a fake site that appears to be legitimate asking for your login credentials. That is the data that has been compromised.