Hi pauldeceglie
welcome to the Apple (user-to-user) Community.
Re: "I was charged for an in-app purchase but i had entered a apple gift card"
Wondering if you actually redeemed the Gift Card ok:
Eg: You might want to check if you have a gift card balance:
Apple Support article: Check your gift card balance
Re: Redeeming a gift card:
Apple support have articles online to help:
How to redeem your Apple Gift Card or App Store & iTunes gift card - Apple Support
and
Seems you would generally be able to buy the in-app purchases ok.
What you can buy with your Apple Gift Card or Apple Account balance – Apple Support
says:
Find out more about how purchases bill to your Apple Account balance
Seems that only if Apple was unable to access the gift-card funds, then your credit card would be charged.
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Re: "I was charged to my credit card instead of the gift card and now im upset"
If you want you can : Report a problem:
https://reportaproblem.apple.com/?s=6
or
Request a refund for apps or content that you bought from Apple
or
You can reach out to the Billing Support Team:
There is a “Get Support” Link (online chat, phone, eMail etc) or a Support App you can download, at the bottom of their webpage.
Subscriptions and Billing - Official Apple Support
All the best :-)