get_flight_cost(travel_from='JFK', travel_to='LAX', travel_date='2024-12-15', travel_class='business')
book_flight(access_token='abc123xyz', card_id='card_2108', travel_date='2024-12-15', travel_from='JFK', travel_to='LAX', travel_class='business')
retrieve_invoice(access_token='abc123xyz', booking_id='3426812')
cancel_booking(access_token='abc123xyz', booking_id='3426812')
send_message(receiver_id='USR006', message='Hi Sam, my travel plans have changed. I\'ll update you soon.')
view_messages_sent()
delete_message(receiver_id='USR006')