In very rare circumstances we have had customers who received what they believed to be more than one charge on their credit card that they used to purchase their item. There a a few reasons this can happen. Some of our customers will place multiple orders within a day and can will separate the transaction. Another reason can be due to a double click when placing an order.
No matter what the issue may be, please contact support at firstname.lastname@example.org and they will investigate the issue and issue any refund immediately where necessary.