Hi, I redeemed my apple gift card to purchase uc in pubg but it won’t allow me to use apple balance. Only option is credit/debit card.

You may see a notice to enter a credit card for "verification purposes" even if you intend to pay using apple ID balance. Enter your card and very likely it will only charge your Apple ID balance as long as you have sufficient money to pay for the item, and leave your card untouched.

You can't select which payment type is used, it is automatically selected for you, Apple ID balance first and then the list of other payment optios you have entered. It will always use Apple ID balance first unless it is one of hte very few kinds of items (such as a gift card) where you can only pay with a card.

I have a credit card on file as well as a gift card balance of $50, but when I try to make a purchase, it only allows to the credit card to work. I can see the option for the gift card balance but it doesn't allow me to select it as a payment option. So now i have $50 of unusable credit. please help...