PO Change Order transmission via cxml format

We are trying to implement punch-out process and PO transmission in cxml format. We are able complete the configuration for Punch-out an cxml transmission of new Purchase Orders. But we are unable to transmit the Change Order details in cxml format.

Our goal is to transmit the PO and change Order Information to Supplier in cxml format and the transmission method as HTTPS.

Options tried:

1. when using the mapping method as "cXML_OrderRequest" and standard code as cxml for both PO and Change orders. New PO information is getting communicated correctly. But for the Change Orders, information is being communicated to the supplier and cxml file is having the original po details. Not the revised information.