Changes to delivery information such as delivery destination or recipient phone number can only be made in the "wait for delivery" state, which is a waiting state in which the order (delivery request) has not been transferred to the seller. In other words, you cannot change the delivery information in the post-delivery request stage.
 

On the detailed page of the product you want to change the delivery information on the My Shopping Information > Transaction Status > View signed order menu, you can modify the recipient's contact and delivery information, and after checking the changes, you can click the Change Shipping Information button at the bottom.

However, even if the delivery information has been changed, the changed information may not be applied if the delivery of the product has already begun.