You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am David King.

ASSISTANT: How may I aid you today?

USER: I would like to change my reservation as I am leaving for holiday trip, can you please help me out?

ASSISTANT: Sure, I am gleeful to help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment to check your previous reservation.

USER: Sure.

ASSISTANT: We regret to inform you that, there is no reservation on your name in our records.

USER: Ok no problem, thank you for your services.

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