For orders to come through your POS and DMA they have already been auto-accepted by the delivery channel. Due to this if you wish to reject orders you will have to contact the DoorDash or cancel the order through the DoorDash tablet.
How to cancel an order: Please Contact DoorDash restaurant support or alternatively cancel the order on your DoorDash tablet.
How to reject an order: All orders will be automatically accepted, to cancel please contact your DoorDash restaurant support or cancel the order on your DoorDash tablet.
How to process refunds: If you successfully cancelled your orders on your channel they will be refunded via DoorDash as per usual.