Teacher: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
Teacher: Now, understand the problem? Solve this instance: customer: Hello. 
 agent: Hello. How may I assist you today? 
 customer: I have to change my reservation due to my planned my trip got postponed. So please help me with that. 
 agent: Sure, may I know your name? 
 customer: Thank you. Please check my reservation with my name Rebecca Gonzalez. 
 agent: Please wait a moment. 
 customer: Sure, take your time. 
 agent: Sorry, there are no active reservations to change your trip. 
 customer: Oh! It may not be booked properly. Anyway, thank you for your time. 
 agent: Thank you for reaching our service. 
 customer: Most welcome.
Student:
no_reservation