You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I want to change my existing reservation. Could you help me with that?

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

USER: Thank you. Gary Perez here.

ASSISTANT: Wait a moment please.

USER: Ok.

ASSISTANT: Gary Perez, 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.

ASSISTANT: Thank you for choosing us.