You can cancel an order and refund the full amount to the customer. Find the order using Orders tool, click to display details and click "Refund order".
Money will be refunded to your buyer within two banking days to the same account which was used to make the purchase.
Reasonable amount of refunds are done free of charge. Contact us for pricing and procedure, in case you plan to cancel the whole event or need to refund more than one hundred orders.