In this task, you are given a conversation between a flight agent and the customer. You are given 4 options and you need to select the goal of the conversation. It is provided as part of customer's context, which has to be one of the following: `book`: Make a new reservation, `cancel`: Cancel an existing reservation, `no_flight`: No flight found for the customer's preference, `no_reservation`: No reservation / No change / No cancellation was made in the conversation, mostly enquiring details

customer: Hello. 
 agent: Hello, how can I help you today? 
 customer: Can you please change my existing reservation due to postpone of my trip? 
 agent: Sure, can I have your name please? 
 customer: My name is William Baker. 
 agent: We found a reservation on your name, can  you please share your new trip dates? 
 customer: My new trip dates are June 20 and June 22. 
 agent: Let me know your airport codes? 
 customer: I am heading to SFO from ORD. 
 agent: Any other requirements to be met? 
 customer: I need a single connecting flight. 
 agent: Sorry, no flights found with your given details. 
 customer: Not a problem, thank you for the information. 
 agent: Thank you for reaching us.
no_flight