Vendor Return

Product is Netsuite, we want to be able to process a credit against an invoice that will recognize that the items on the purchase order have not actually been purchased.  ACS team is telling us that isn't possible and that the solution is to create new lines on the PO.  Unfortunately, this causes disconnects b/w our Statements of Work or Quotes and the PO.  We don't think this would pass a SOX audit.  More importantly, it re-routes the large purchase orders back to our Executives.  Has anyone else experienced something similar?  I find it hard to believe that this wasn't