How to reverse/change SRM PO with status "transaction completed"

We use Extended Classic scenario in our company.      There is a PO has outstanding G/R balance,   but user accidently hit the button "complete"on this PO  in SRM ,   in result the PO has been completed with status "transaction completed".    And nothing can be performed on this PO.   

G/R balance is out there and now it has financial impact as it blocked the funding thru internal order. 

Anyone have idea how we can resolve this problem.    Can we reverse/change the PO status?   Please note G/R canu2019t be entered in ECC as restricted.  

Thanks,

Frieda

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