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 may I be at your service today? 
 customer: Due to some entrepreneurship meeting, I am going to change my existing reservation. 
 agent: May I know your name please to check the status of your reservation? 
 customer: Sarah Lopez here. 
 agent: Thank you. Please stay online for a while, I will check your reservation status and let you know. 
 customer: Sure. 
 agent: Sorry, there is no reservation matching with your name in our portal to make changes further. 
 customer: No problem, thanks for the information. 
 agent: Thank you for reaching us.
no_reservation