unable to create BOL core entity

Hi Experts,

I want to create a new BuilContactPerson entity, however I've been unable to figure out what I am doing wrong.

DATA: lt_params TYPE crmt_name_value_pair_tab,
       ls_params TYPE crmt_name_value_pair,
       lv_bol_core TYPE REF TO cl_crm_bol_core,
       lv_relation_factory TYPE REF TO cl_crm_bol_entity_factory,
       lv_relation TYPE REF TO cl_crm_bol_entity,
       lv_transaction TYPE REF TO if_bol_transaction_context.

ls_params-name = 'CONT_PERS'.
ls_params-value = '0009000185'.
APPEND ls_params to lt_params.
ls_params-name = 'BP_NUMBER'.
ls_params-value = '0000000110'.
APPEND ls_params to lt_params.

lv_bol_core = cl_crm_bol_core=>get_instance( ).
lv_bol_core->start_up( 'BP_APPL' ).

lv_relation_factory = lv_bol_core->get_entity_factory( 'BuilContactPerson' ).
lv_relation = lv_relation_factory->create( lt_params ).

lv_bol_core->modify( ).
lv_transaction = lv_bol_core->get_transaction( ).
lv_transaction->save( ).
lv_transaction->commit( ).

Any helpful hints will be rewarded. Thank you in advance.