You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: I am David Wilson. I want to change my existing reservation, due to heavy rainfall in Seattle, can you help me in changing the reservation?

ASSISTANT: Sure, please wait for a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no reservation found on your name in our database to change.

USER: That's ok, thank you for your information.

ASSISTANT: You are welcome.