My gift card with $10 appstore credit and my debit card were both charged when i made a $10 inapp purchase

When i went into an app to make a inapp purchase i had a $10 appstore gift card that i put on my account, i went to make the inapp purchase of 9.99 and when i went into my debit card purchases and i saw that my debit card was charged for $9.99 inapp purchase then i went into the appstore to look at my appstore credit and it said i had 0.00. So both my debit card and store credit were charged when i made an inapp purchase. This is really bad if im getting charged for 2 things yet only 1 of the two should have been charged. i found another question on the discussions page for apple and i fixed my account so hopefully next time it doesnt do that but i want my money back on the purchases that got charged for my store credit and debit card how should i go about doing this becuase it should be apples problem for billing me on both.