Redeeming credits on iTunes
I am on Family Sharing. My children have asked to purchase apps from the app store. When requesting an app I have signed in with my Apple ID to approve their purchase. The purchases keep showing up on my credit card. I have over $60 credit available on iTunes. I was under the impression that it would automatically take redeemed gift card credits before charging my credit card. This is very frustrating. How can I change this?
Thanks