Multi-turn user requests:
user: I need to schedule a flight soon and want to examine different alternatives. Calculate the cost of a business class ticket for the first airport on the available list to the last airport on the same list. Provide the estimated total payable amount for me.
user: The booking id is 1234 and the travel date is the last day of October 2024.
user: After determining the flight prices, arrange to reserve a business class seat with those specifics using my card with id main1234 and authorization token 'abc123xyz', once you've gotten full approval.
user: Security matters to me, therefore purchase a comprehensive $769 travel insurance policy for this trip using my card immediately after the booking is confirmed.
user: Following the insurance purchase, send me a detailed bill for this reservation and outline all incurred charges.
user: There's an urgent matter I need solved. Reach out to customer service for me and relay my booking-related query.
user: However, I've opted to annul the trip. Conduct the requisite steps to cancel the booking and make sure my card receives a refund.

Tools involved: TravelAPI
Expected function-call sequence: TravelAPI.list_all_airports
TravelAPI.get_flight_cost
TravelAPI.book_flight
TravelAPI.purchase_insurance
TravelAPI.retrieve_invoice
TravelAPI.contact_customer_support
TravelAPI.cancel_booking