You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: Owning to an emergency, I want to change my existing reservation. Can you help me?

ASSISTANT: Sure, I am here to help you with that. Please wait for a moment.

USER: Sure.

ASSISTANT: May I know your name please?

USER: Ok, I am Dennis Mitchell.

ASSISTANT: Sorry Dennis, no reservation found by your name in our database.

USER: That's fine, no problem. Thank you for your information.

ASSISTANT: It's my pleasure.