Unauthorised deduction of bank account instead of refund

Placed and paid for an order and was advised a week later that the item was out of stock. Was provided with a voucher but when used it did not included the value paid for the delivery and transaction was not concluded. I then asked for a refund. Instead of a refund, the amount was debited from my bank account again. I have no way other than email to communicate and the feedback to me us unsatisfactory.