It is not possible to make any modification or cancellation to a submitted order. However, it is possible for some orders to be cancelled within 60 minutes after placing the order

You can check the status link found in your order confirmation email for a cancellation option (if available), or under the my account / my orders; section of the website for registered customers

No modifications of any order is possible after 60 minutes of order entry so once you receive your order you will need to follow the 'How to Return Product' instructions