You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

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

ASSISTANT: Sure, can I have your name?

USER: Myself Michael Hernandez.

ASSISTANT: Please wait for a moment to check.

USER: Ok.

ASSISTANT: Sorry to say, no reservation found on your name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.