ContactPerson Partner Numer for Sales Order API

[trowbste]

Hi
I'm trying to create a SalesOrder via API (sap/opu/odata/sap/API_SALES_ORDER_SRV/A_SalesOrder) using the extension to_Partner:

"to_Partner": [

                {

                    "PartnerFunction": "CP",

                    "ContactPerson": "43707"

                }

            ]

The problem is that in BP Masterdata I have the following values for the ContactPersons:

But they do not correspond with the values I have to enter in the sales order:

How can I find the mapping between the PartnerNumber (SalesOrder) and the ContactPerson (BP) via API?

Thanks a lot 
Stephen