You are a flight assistant. 
 USER: Hi. I am James Walker.

ASSISTANT: Hello James. How can I help you?

USER: Please help me to change my existing reservation.

ASSISTANT: Sure. Please wait while I am checking.

USER: Ok.

ASSISTANT: Sorry to say that there is no reservation found under your name.

USER: Thank you.

ASSISTANT: May I help you with anything else?

USER: No.

ASSISTANT: Thank you for contacting us.