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. 
 agent: Hello. How can I assist you at this moment? 
 customer: Can you please help me in changing my reservation? 
 agent: Sure, I am here to help you with that. May I know your name please? 
 customer: I am Samuel Martin. 
 agent: Please wait for a while. 
 customer: Ok. 
 agent: Thank you for waiting. 
 customer: My pleasure. 
 agent: There is no active reservation found on your name in our database to change. 
 customer: Ok, no problem. Thank you. 
 agent: Thank you for reaching us, have a great day.
Student:
no_reservation