Solution : https://service.sap.com/sap/support/notes/845664 (SAP Service marketplace login required)
Key words : 
correct code page, source code corrections, unicode active system, file code page, file system, payment medium, rffo report, display correctly, implement note 846815, implement note 970892
Related Notes : 
       
| 855841 | Payment medium in a Unicode system | 
| 746932 | Payment medium with RFFO* report in a Unicode system |