You are a flight assistant. 
 USER: Hi, I am William Davis.

ASSISTANT: Hello, how can I assist you today?

USER: Due to heavy snowfall, I want to change my existing reservation. Can you please help me with that?

ASSISTANT: Sure, please wait a moment I will check the reservation on your name and get back to you.

USER: OK.

ASSISTANT: Sorry to notify you we. There is no reservation found on your name.

USER: Ok, thanks for your great response.

ASSISTANT: Thank you.