Problem with BAPI_SALESORDER_CHANGE changing VBAK-LIFSK

Hi experts,

I need to update sales order delifery block (VBAK-LIFSK) within a report. I am using bapi BAPI_SALESORDER_CHANGE like this:

data: gv_header_in TYPE bapisdh1,

gv_header_inx TYPE bapisdh1,

i_return TYPE bapiret2_t.

gv_header_in-dlv_block = p_lifsk.

gv_header_inx-dlv_block = 'X'.
gv_header_inx-updateflag = 'U'.

CALL FUNCTION 'BAPI_SALESORDER_CHANGE'
EXPORTING
salesdocument = p_datos-vbeln
order_header_in = gv_header_in
order_header_inx = gv_header_inx
* logic_switch = gv_logic_switch
TABLES
return = i_return.

But I always get an error even when I do the same in VA02 (and in VA02 works fine).

One of these errors is V1 739 (Field '&1' cannot be changed, &2 &3 &4 ready for input), although in VA02 this field is editable.

Another one is CZ 280 (Sales office &1 is not assigned to sales organization &2).

Do I have to pass to the bapi any other data?

Thanks!

Maria