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: I want to change my existing reservation which is done recently due to business meeting postponed, can you please help me? 
 agent: Sure, can you give me your name for changing purpose? 
 customer: Ok, my name is Brian Campbell. 
 agent: Ok, please be on hold, let me check for the availability. 
 customer: Ok, please check it. 
 agent: Sorry, Campbell there is no reservation found on your name. 
 customer: Ok, no issues. 
 agent: Thank you for approaching us. 
 customer: Anyways, thank you for your service.
no_reservation