You can cancel any unshipped items or orders from your Manage orders page. After you cancel an item or order, Amazon will send a cancellation email to the buyer.
You can also cancel multiple orders using one of the following techniques:
Occasionally, you may need to cancel part of an order with multiple items and refund the items that are cancelled. If you manage your orders using inventory files, you can upload an Order Adjustment Feed.
To cancel or refund part of a multi-item order, follow these steps: