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: Hi, I am Stephen Evans. 
 agent: Hello,. How may I help you? 
 customer: I want to change my reservation, can you help me with that? 
 agent: Please wait a moment. 
 customer: Sure. 
 agent: Sorry, no reservation found by your name. 
 customer: Thanks for the information. 
 agent: Thank you.
no_reservation