A supplier can cancel an order and trigger a refund of the wholesale amount by clicking "More actions" -> "Cancel order" in their Shopify admin. This will cancel the order and refund the amount charged to the retailer's credit card. At this point, the supplier should contact the retailer to refund the order to the customer.
The retailer can also choose to cancel and refund the customer first, they will just need to contact the supplier to refund the amount owed to them.
NOTE: A customer will not be refunded until the Retailer also refunds the order.
NOTE: The customer and the supplier are refunded the full payment, however, the retailer is not refunded for Carro's 5%.