If you booked a reservation, you can cancel through the app 1 hour before the pickup time. Go to Menu -> Order List -> Reservation List. Choose the reservation you want to cancel then click [Cancel Booking] to cancel.
If you wish to cancel immediate orders or booked reservations less than 1 hour before pickup time, Go to Menu -> Order List -> History/Reservation List. Choose the order you want to cancel then click [Inquire by Phone] to request for cancellation.