Netsafe Said:
"Wrong gift card balance: I bought a $50 gift card and when I redeemed it, it was showing less than that amount. The amount is showing as $36.13 and I haven't even used it yet. How do I fix this? Why is this happening? Should one of the steps be to go to the store I bought it from and ask them?"
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What to do from here:
See if something that was overdue was automatically deducted. Check Here: View your Purchase History for the App Store or iTunes Store - Apple Support
As for verifying the amount, take this up with the seller. Take it back to the store, long with the receipt and show them this transaction using your hand held device (i.e. iPhone or Android).
In all, take this as a learning experience - next time you purchase such a card, add it to your account right then-and-there as soon as the transaction goes through. These are user-to-user forums - deal with the seller to get your money back.