There is a $13 charge on my creadit card each month. What is it for

That’s unfortunate. If you go to the App Store on your iPhone then navigate to the updates page then click your account info then click manage subscriptions you might see the problem there if not it could be iCloud storage that you are buying or it is not Apple taking Money from you but someone else using there name

You can follow the steps here to view any recurring subscriptions you may have on your account: View, change, or cancel your subscriptions - Apple Support