Wrong WBS assigned in Purchase Requisition

Hi Gurus !

I was creating Purchase Requisition for a Project but by mistake took the WBS of another project in CJ20N ( Project Builder ) , and the PO has been made , even the GRN is also over . When Iam trying to open any S_ALR report it is showing 2 networks with different activities in one project.

I.R. ,Invoicing and GRN can't be reversed as booking period is already closed .

Please tell me how to correct it ? ?