What happens if a customer returns or cancels an order?

You must handle the communication with the customer about their order yourself. If the customer has canceled or returned their order, simply go into your shop system or payment gateway and refund/credit the order. 

We then automatically offset the amount of the order in a later payment. We will of course refund the amount to the customer's ViaBill account. If the customer has already paid for the order in question and does not otherwise have an outstanding ViaBill, we will refund the amount to the customer's bank account.