Given the task definition and input, reply with output. 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. 
 agent: Hello, how can I serve you today? 
 customer: Can you help me to change my recent reservation? 
 agent: Sure, I am glad to help you. 
 customer: Thank you. 
 agent: May I know your good name to proceed further? 
 customer: My name is Nancy Williams. 
 agent: Please be on hold. I will check in the list and revert you. 
 customer: Sure. 
 agent: There is no reservation found on your name in our database. 
 customer: It's ok, thank you for checking. 
 agent: Thank you for availing us.
no_reservation