You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

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

ASSISTANT: May I know your name please?

USER: Gary Walker.

ASSISTANT: Please wait.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name to change.

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

ASSISTANT: Thank you for reaching us.