That is a phishing scam. 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
In the future if you are unsure whether a charge is real you can use the following to see purchases on your account:
Get help with an item purchased from the App Store, iTunes Store, or iBooks Store - Apple Support
and: If you see 'itunes.com/bill' or an unfamiliar charge on your statement - Apple Support