You are able to refund a customer through the Promotion Centre. To do this head to the Dashboard and click 'Sell Tickets' > 'View My Tickets'. Under the event you'd like to process a refund on, click 'Order Admin'.
The order admin screen will then pop up, from here you can search for a customer's name. Once you've found the customer, you can access their order by clicking either their Order ID or the magnifying glass icon to the far right.
Here you will see your customer's full order details. This page will give you the option to refund the customer to the card they originally purchased tickets with and will take up to 5 working days to clear into their account.