Hi,
Check this sample program ---
REPORT ztest_sumeet1.
DATA : lt_pd_imp TYPE crmt_partner_external_wrkt.
DATA : ls_pd_imp TYPE crmt_partner_external_wrk.
DATA : lv_guid TYPE crmt_object_guid.
DATA : lt_header_guid TYPE crmt_object_guid_tab.
lv_guid = '02DAF32691311ED285D62D9702253141'.
INSERT lv_guid INTO TABLE lt_header_guid.
CALL FUNCTION 'CRM_ORDER_READ'
EXPORTING
it_header_guid = lt_header_guid
IMPORTING
et_partner = lt_pd_imp.
DATA : pguid TYPE bapibus1006_head-partnguid.
DATA : bpout TYPE bapibus1006_head-bpartner.
LOOP AT lt_pd_imp INTO ls_pd_imp.
pguid = ls_pd_imp-bp_partner_guid.
CALL FUNCTION 'BAPI_BUPA_GET_NUMBERS'
EXPORTING
businesspartnerguid = pguid
IMPORTING
businesspartnerout = bpout.
CHECK sy-subrc = 0.
ENDLOOP.
Its working for me !!!
Regards,
Sumeet