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 assist you? 
 customer: Owing to emergency, my planned trip to New York to attend a workshop on SAP has been postponed. So I want you to change my existing reservation? 
 agent: May I know your name? 
 customer: Sure, I had a reservation with name Stephanie Carter. 
 agent: Please wait a moment. 
 customer: Sure. 
 agent: Sorry, there is no reservation found on your name. 
 customer: Ok, no worries at all. 
 agent: Thank you for choosing us. 
 customer: Thanks for your kind service.
no_reservation