Why do I keep getting charged for iTunes ?

If you are constantly being charged at the same rate and the same amount you likely have a subscription you forgot to cancel. Most "free trials" continue as a paid membership if you forget to cancel

You can check and cancel your subscriptions here

See or cancel your subscriptions – Apple Support

Possibly a subscription if it is a recurring charge for the same amount. See: See or cancel your subscriptions - Apple Support

Another possibility for a recurring charge is for an upgrade from the free 5GB iCloud storage. To see what storage you have and to downgrade if desired, see: Downgrade your iCloud storage - Apple Support

If neither of the above help, review all of the steps in If you see "apple.com/bill" or an unfamiliar charge on your statement - Apple Support

That link includes information on contacting Apple Support if the other steps don't help.