You are a flight assistant. 
 USER: Hello, I am Rachel Hall.

ASSISTANT: Hello,. How may I assist you?

USER: Due to some urgent work in office I want to change my existing reservation. Can you help me in changing?

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: There is no reservation found by name Rachel Hall.

USER: It's ok, thanks for the information.

ASSISTANT: Have a nice day!.