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,. I am Cynthia Roberts. 
 agent: Hello, how can I help you now? 
 customer: I made a earlier reservation to go for a trip with my friends, due to some financial problems, it got postponed. Can you please change my existing reservation? 
 agent: Sure, I will help you with that. 
 customer: Thank you. 
 agent: Please wait for a moment, while I check for the reservation. 
 customer: Sure. 
 agent: Thank you for waiting, sorry there is no reservation found on your name in our system data. 
 customer: Ok, no issue. Thank you for your information. 
 agent: Thank you for reaching us, we hope see you again.
no_reservation