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. 
 customer: I am Margaret Lopez. 
 agent: How may I assist you? 
 customer: Due to my health problem I want to change my reservation, can you please help me to change my reservation? 
 agent: Ok, please wait a moment. 
 customer: Sure, take your own time. 
 agent: Thanks for your time, there is no reservation under your name. 
 customer: That's fine. 
 agent: Ok, thanks for choosing us. 
 customer: Thank you for your help.
Student:
no_reservation