Function module SD Sales Order Status Header and Items - SAP

       FM1: To get Header Status list

CALL FUNCTION 'RV_DOCUMENT_HEAD_STATUS_TEXTS'
        EXPORTING
          vbuk_in       = ls_vbuk
          window_senden = space
        IMPORTING
          vbstt_wa      = ls_vbstt.

Pass Sales order to structure VBUK_IN and will give us Status tab information in sales order Header

FM2: To get Item Status list

    CALL FUNCTION 'RV_DOCUMENT_POS_STATUS_TEXTS'
      EXPORTING
        vbup_in       = ls_vbup
        vbuk_in       = ls_vbuk
        window_senden = ''
      IMPORTING
        vbstt_wa      = ls_vbstt_pos.

Pass Sales order and required line item status to structure VBUP_IN and will give us Status tab information in sales order respective item