BAPI_PR_CHANGE how to add account assignment information for the existing service line ?

[wanghb]

sap abap BAPI_PR_CHANGE change the account assignment category and item category from U、D to T、D，for the same time, fill the account assignment information：gl account、WBS、cost center in the existing service line, but the bapi return always failed, the PR's instance has not changed, it's no extra information, please help to resolve the question, below is the part of my code, thanks.

praccount = tab_praccount 

praccountx = tab_praccountx

rec_praccount-PREQ_ITEM = '00010'.

rec_praccount-serial_no = '01'.

rec_praccountx-PREQ_ITEM = '00010'.

rec_praccountx-serial_no = '01'.

rec_praccountx-PREQ_ITEMX = 'X'.

rec_praccountx-serial_nox = 'X'.

************************************************

servicelines = tab_service

servicelinesx = tab_servicex

rec_service-DOC_ITEM = '00010'.

rec_service-OUTLINE = '0000000001'.

rec_service-SRV_LINE = '0000000010'.

rec_servicex-DOC_ITEM = '00010'.

rec_servicex-OUTLINE = '0000000001'.

rec_servicex-SRV_LINE = '0000000010'.

************************************************

serviceaccount = tab_serviceaccount

serviceaccountx = tab_serviceaccountx

rec_serviceaccount-DOC_ITEM = '00010'.

rec_serviceaccount-OUTLINE = '0000000001'.

rec_serviceaccount-SRV_LINE = '0000000010'.

rec_serviceaccount-SERIAL_NO = '01'.

rec_serviceaccount-SERIAL_NO_ITEM = '01'.

rec_serviceaccountx-DOC_ITEM = '00010'.

rec_serviceaccountx-OUTLINE = '0000000001'.

rec_serviceaccountx-SRV_LINE = '0000000010'.

rec_serviceaccountx-SERIAL_NO = '01'.

rec_serviceaccountx-SERIAL_NO_ITEM = 'X'.

************************************************