You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I am happy to help you with that. Can I have your good name please to check your reservation status?

USER: I am Jack Walker.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry Jack Walker, no reservation has found under your name to change.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us, have a good day.