Close PO - return item

Hi

I have a problem with close PO. I made PO with Return item, and has been made also GR. but there were some problems and i need to cancel GR for this PO. no new GR has been made.

Problem is how to close PO in this situation, while i try to put Delivery completed or Delete this line, but every time i have notification - item reserved, no changes allowed.

Please help

tnx

Marina