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: Hi. 
 agent: Hello, how can I help you? 
 customer: Can you please change my recent reservation? As my planned trip has been postponed to some other dates. 
 agent: Yes, I am here to help you. May I know your name please? 
 customer: Sure, my name is Gary Hall. 
 agent: Ok, please wait a minute. 
 customer: Sure. 
 agent: Thank you for your time, sorry no reservation found on your name. 
 customer: That's ok, thank you for giving the information anyways. 
 agent: Thank you for reaching us, have a nice day.
no_reservation