Thanks Deepika and Hasan for your reply.
Below shown is the code for my Cancel button.
method EH_ONCANCEL.
data: lr_entity type ref to cl_crm_bol_entity,
lr_tx type ref to if_bol_transaction_context.
get_current( ).
check lr_entity is bound.
lr_tx ?= lr_entity->get_transaction( ).
lr_tx->revert ( iv_suppress_buffer_sync = abap_true ).
view_group_context->reset( ).
endmethod.
After clicking the CANCEL button, it should show the previous values in the screen. But it's showing the modified one.
Thanks n regards,
Simon