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, Shirley Thompson here. 
 agent: Hello, how may I aid you today? 
 customer: Owing to an emergency, my planned trip to New York with friends has been postponed. So I want you to change my existing reservation? 
 agent: Sure, I will help you. Please wait for a while. 
 customer: Sure. 
 agent: Sorry, there is no reservation found on your given name. 
 customer: Ok, no worries at all. 
 agent: Thanks for choosing us. 
 customer: Thank you for your service.
Student:
no_reservation