You are a flight assistant. 
 USER: Hoi.

ASSISTANT: Hello, how may I help you?

USER: I am David Davis. I need to change my existing reservation as my exams got postponed, Can you please help me with that?

ASSISTANT: Sure, I am here to help you. Please wait for a moment to check your details.

USER: Sure.

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

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us, have a nice day.

USER: Thanks for your information.