Why was I charged for $19.98

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. 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

You can use the following instructions to determine if it is a real charge, what it is for, and to report a problem: Get help with an item purchased from the App Store, iTunes Store, or iBooks Store - Apple Support

Also see: If you see 'itunes.com/bill' or an unfamiliar charge on your statement - Apple Support

Just in case, check subscriptions > View, change, or cancel your subscriptions - Apple Support

If it turns out that's not the issue, try here > If you see 'itunes.com/bill' or an unfamiliar charge on your statement - Apple Support

What indicates to you that you have been charged? Was it simply an email, or do you see a charge on your payment account?

If it is an email it is likely a phishing attempt: Identify and report phishing communications - Apple Support

If it is on your statement: iTunes charges not recognized

Best of luck,

GB