Teacher: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
Teacher: Now, understand the problem? Solve this instance: customer: Hi. This is Michelle Clark, from Dallas. 
 agent: Hello, How may I assist you? 
 customer: Recently I made a reservation and now the trip has been postponed due to some issues. Can you help me in changing my ticket? 
 agent: Sure, I can help you. 
 customer: Thank you. 
 agent: Please wait for a while. 
 customer: Sure. 
 agent: Thanks for your time, there is no reservation found in your name. 
 customer: That's ok, not an issue. Thanks for your effort. 
 agent: Thank you for choosing us.
Student:
no_reservation