You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: I want to change my existing reservation due to postpone of my exams. Can you help me in that?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: May I know your good name please?

USER: Amy Lopez here.

ASSISTANT: Please wait for a moment, while I check for the reservation.

USER: Ok.

ASSISTANT: Thank you for the details, sorry there is no reservation found on your name in our system data.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for visiting us, we hope see you again.