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 and access token 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: The credit card ID is card_6789 and the access token is 'abc123xyz'.
user: Post-booking, pondering added precautions, getting travel insurance seems wise, aiming for a coverage sum of $100,000 costing half of its coverage. 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