How do I remove "Request Changes" from Action drop-down in iSupplier?

I am trying to disable the supplier's ability to request changes to a PO that has been issued to them.  On the "Orders" tab I have disabled the "PO Change" button by switching "Rendered" from "Inherit" to "False" under Personalize Page, however if I open up a specific PO the option to request changes exists in the "Action" menu.  I have hunted through the personalization options for that page, but I have been unable to locate how to remove an option from the drop-down menu.  How can I remove this?