PO is in Open we are unable to unassigned the Blanket Purchase Agreement

Summary:

PO is approved and in Open status, it has BPA assigned to it. Now we want to disassociate the BPA manually but when we edit the PO ,we found the BPA field is unedited mode.

Content (required):

Version (include the version you are using, if applicable):

23c

Code Snippet (add any code snippets that support your topic, if applicable):