If you made a purchase at the store how could it be the wrong store? Anyway you would have to return it to the store. If it's an online purchase you can go into the order to cancel it.
You will have to return the item back to the store and meet a customers services agent that will give you a form to fill for the refund of fund back to your card. Alternatively, call Wal-Mart customer service number for best advice.
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