Why am I being charged for free apps when it's time for the apps to be updated?
Why am I being charged a fee to update free apps?
There normally is no fee to update a free app. You may want to reply with more details about the apps in question and about why you believe there is a fee. Also, you may want to review what your purchase history shows -- i.e., is it showing the fee and how is the charge described: See your purchase history in the iTunes Store on a Mac or PC - Apple Support