For International Orders: 
Once an order has been completed, the order items cannot be changed.

For Domestic Orders:
Once an order has been completed, we are unable to accept the following changes:

• Changes to items (including type or size)
• Changes to quantity
• Partial cancellations

If you would like to change the items in your order, please cancel your order and place a new order with the desired items.
For instructions on how to cancel your order, please refer to the Help page “Canceling an Order.”

You may add items to your order (merge orders) only if the shipment status is “Order received.”
For detailed instructions, please refer to the Help page “Adding an item to an existing order (merging orders).”