BAPI_PO_CHANGE - add serial

Hello!

I'm trying to add a serial number to position in order.

Using  BAPI_PO_CHANGE.

(Order is created and has single position without serial number. Component structure has 1 line with batch filled)

I'm filling mt_serialnumber from a scratch:

           <fs_serialnumber>-po_item = '00010'.

           <fs_serialnumber>-sched_line = '1'.  

           <fs_serialnumber>-serialno = '919191'.

           <fs_serialnumberx>-po_item = '00010'.

           <fs_serialnumberx>-sched_line = '1'.

           <fs_serialnumberx>-po_itemx = 'X'.

           <fs_serialnumberx>-sched_linex = 'X'.

           <fs_serialnumberx>-serialno = 'X'.

I get mt_item, mt_comp structures from FM BAPI_GETDETAILS1.

+ add some new data:

<fs_itemx>-po_itemx   = 'X'.

<fs_comp>-batch = 'P0000010'. "new batch according serial

<fs_compx>-batch = 'X'.

and starting BAPI:

CALL FUNCTION 'BAPI_PO_CHANGE'

       EXPORTING

         purchaseorder = mv_ebeln

         poheader      = ms_header

         poheaderx     = ms_headerx

       TABLES

         return        = lt_return

         poitem        = mt_item

         poitemx       = mt_itemx

         pocomponents  = mt_comp

         pocomponentsx = mt_compx

         serialnumber  = mt_serialnumber

         serialnumberx = mt_serialnumberx.

CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'

         EXPORTING

           wait = 'X'.

But no update

lt_return has no errors (S and couple minor W)

Maybe I only able to CHANGE data with this BAPI, not adding new lines? Hm.

Any clues?

Best regards,

Maxim.