You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I assist you today?

USER: Please change existing reservation. I am Elizabeth Davis.

ASSISTANT: Please wait a while I will check and let you know.

USER: Sure.

ASSISTANT: Thank you for waiting. sorry, we did not found any reservation on your name.

USER: Thanks for the help.

ASSISTANT: Thank you for reaching us.