Multi-turn user requests:
user: I need to schedule a flight soon on booking id 1234 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, on the last day of October 2024. Provide the estimated total payable amount for me.
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 its 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