An organization gift cannot be changed to a constituent record. You will need to process an offline refund then process and offline gift on a constituent record.

~Refund an Organization Gift 
https://www.blackbaud.com/files/support/helpfiles/luminate-online/help/luminateonline.html#../Subsystems/Constituent360/Content/Tasks/Admin_OrgGifts_Refund.html 

~Enter a gift to the event 
https://www.blackbaud.com/files/support/helpfiles/luminate-online/help/luminateonline.html#../Subsystems/TeamRaiser/Content/Tasks/Admin_TeamRaiser_Gifts_Event_Creating.html