How to Change Sales person Number on existing Billing document

Hi,

Do you want to change sales person ID or EAN number.

The filed which you are referring seems to be European article number. Check below help link on this.

http://help.sap.com/saphelp_470/helpdata/en/12/084876470311d1894a0000e8323352/content.htm

http://help.sap.com/saphelp_45b/helpdata/en/35/6f2939268b2239e10000009b38f984/content.htm

And, i am not sure about changing the sales person ID.

Regards, Sai Krishna.