Customer Account Statement Does not show SAP document number

Hello,

I want to have the SAP-document number on a customer-statement printed with report RFKORD11. I changed the used form now multiple times without success. If I enter the BSID-BELNR as an output parameter the system always gives me BSID-XBLNR what makes no sense to me!

If I look into the table the field is maintained correctly and I really have no idea why the system is always taking the XBLNR-content. If it output XBLNR I am getting the XBLNR-content but not the other way round...

Maybe it is a stupid problem but I have no idea why it works that way and I need the SAP-document number printed on the customer-statement. The other table RF140 does not offer me the document-number as a field.

Thanks in advance for all hints and solutions!

Regards,

Steffen