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

ASSISTANT: Hello, how can I assist you?

USER: As an emergency work in hospital got postponed I want to change my existing reservation. Can you help me in that?

ASSISTANT: Sure, we are here to help you. Please wait for sometime, I will check and revert to you.

USER: Ok.

ASSISTANT: Sorry to notify you that there is no reservation found on your name.

USER: Ok, Thanks for the information.

ASSISTANT: Thank you.