You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Joshua Lee.

ASSISTANT: How may I guide you today?

USER: I would like to change my existing reservation, can you help me in that?

ASSISTANT: Sure, I will help you with that.

USER: Thank you for accepting my request.

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

USER: I will  wait for your response.

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

USER: That's ok, no problem. Thank you for the information.

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