You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you for the day?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, I am here to help you with that. May I know your name please?

USER: I am Joseph Walker.

ASSISTANT: Please wait for a while, let me check your previous reservation status.

USER: Ok.

ASSISTANT: Thank you for waiting. There is no reservation found on your name in our database to change.

USER: Ok, no problem. Thank you.

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