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: Hello. 
 agent: Hello, how can I help you today? 
 customer: I want to change my existing reservation due to sudden demise of my grand father. Can you please help me with this? 
 agent: Sure, may I know your name? 
 customer: Sure, William Perez. 
 agent: Please wait a moment. 
 customer: Ok. 
 agent: Sorry to say, no reservation found with your name. 
 customer: Ok, not an issue. 
 agent: Thanks for reaching us. 
 customer: Thank you for checking.
Student:
no_reservation