delete line within BAPI_SALESDOCUMENT_CHANGE

Hi ;

I am working on the BAPI_SALEDOCUMENT_CHANGE trying to delete line item with type 'ZTDC' from sales order.

For this purpose, I am writing a program bellow and I am calling BAP_TRANSACTION_COMMIT FM.

Unfotunately, nothing is changed with no return error. can you help me to understand what's wrong in my program!

header_ch_inx-UPDATEFLAG = 'U'.


select * from vbap INTO CORRESPONDING FIELDSOFTABLE it_vbap
   WHERE vbeln eq v_vbeln and PSTYV eq'ZTDC'.


loopat it_vbap.

     header_ch_inx-updateflag = 'U'.
     item_ch-itm_number       = it_vbap-POSNR.

   item_ch_inx-ITM_NUMBER = it_vbap-POSNR .
   item_ch_inx-UPDATEFLAG = 'D'.
APPEND item_ch_inx.

ENDLOOP.

CALL FUNCTION'BAPI_SALESDOCUMENT_CHANGE'"BAPI Change Sales Document
   EXPORTING
     salesdocument    =   v_vbeln       " bapivbeln-vbeln  Sales and Distribution Document Number
     order_header_in  =   header_ch       " bapisdhead1   Sales Document Header
     order_header_inx =   header_ch_inx         " bapisdhead1x  Sales Document Header Checkbox
*   simulation = SPACE          " bapiflag-bapiflag  Simulation Mode

   TABLES
     return  =   return_ch            " bapiret2      Return Code
     item_in =   item_ch                " bapisditem    Sales and Distribution Document Item
     item_inx =  item_ch_inx                " bapisditemx   Sales Document Item Checkbox