Did you actually pay for this subscription? See this article to view your recent iTunes purchases: See your purchase history in the App Store or iTunes Store - Apple Support
If you received this charge notification in an email, it could be a phishing attempt: Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support
If you did, see this article for help with cancelling Apple-based subscriptions: View, change, or cancel your subscriptions - Apple Support
If your subscription is not billed through Apple, see this article: Get help with subscriptions not billed through Apple - Apple Support
To contest a charge with a subscription billed through Apple, see this link: Get help with an item purchased from the App Store, iTunes Store, or iBooks Store - Apple Support
Sorry, that's a lot of links! 😁