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, I am Donald Moore. 
 agent: Hello, How can I aid you? 
 customer: I need to change my existing reservation as my dates of trip are postponed. 
 agent: Ok. 
 customer: Will you help me in changing my reservation. 
 agent: Sure. Please wait a minute. 
 customer: Sure. 
 agent: Thanks for waiting, There is no reservation found with your name. 
 customer: Ok, thank you for kind service. 
 agent: Thank you.
no_reservation