You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am Joseph Brown. Can you help me in changing my recent reservation?

ASSISTANT: Sure, I am here to help you out.

USER: Thank you.

ASSISTANT: Wait a moment please. Joseph Brown, we regret to inform you that there is no reservation found on your name in our records.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.