Multi-turn user requests:
user: I plan to book a flight from Crescent Hollow to New York, aimed at a business endeavor. Utilize my typical credit card (ID=card_6789) and access token 'abc123xyz' for the payment. Schedule it for economy class on November 12th 2024, making sure my frequent flyer discount is applied, ensuring the total fee is $850.
user: Post-booking, pondering added precautions, getting travel insurance seems wise, aiming for a 100 insurance. Proceed with organizing this with identical travel specifics, and the previously mentioned credit card should facilitate payment.
user: For clarity on financial allocations, I need to gather the invoice that details my recently acquired flight and insurance.
user: Given sudden itinerary conflicts, there's a pivot. Inform customer support of my potential adjustments or explore full refund possibilities because of a family emergency.

Ground-truth function call sequence:
TravelAPI.get_nearest_airport_by_city
TravelAPI.book_flight
TravelAPI.purchase_insurance
TravelAPI.retrieve_invoice
TravelAPI.contact_customer_support
TravelAPI.cancel_booking