You will be given a definition of a task first, then some input of the task.
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 may I assist you? 
 customer: Actually, my friend book a flight ticket in economy class instead of business class. Can you please help me in changing of my existing reservation? 
 agent: Sure, may I know your good name please? 
 customer: Myself Catherine Wilson. 
 agent: Please wait for a moment. 
 customer: Ok. 
 agent: Sorry, there is no reservation found on your name in our database to change. 
 customer: Ok, no problem. Thank you for your information. 
 agent: You are most welcome.
Output:
no_reservation