You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello.

USER: I am Steven Hill.

ASSISTANT: How may I help you today?

USER: I want to change my reservation due to postpone of my international conference at Houston. Could you modify it?

ASSISTANT: Sure, I am happy to help you.

USER: Thank you.

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

USER: Ok, thank you.

ASSISTANT: Thank you for reaching us.