Unfortunately, once shipped in the system the Shipping in an un-reversible step. The recommended way to manage these situations is to create an RA for the goods on the order and enter 'duplicate order ' or something other descriptive as the reason for the return in Blast Ramp
If you have access to the utilities tab, there is a tool to create a Return directly from an order.
Please follow this link on how to create a RA https://help.blastramp.com/hc/en-us/articles/208103496-Create-a-Return