You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

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

ASSISTANT: Sure, could I have your name please?

USER: Myself Larry Taylor.

ASSISTANT: Ok, please allow me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: You are welcome, have a great day.