You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: My name is Stephen Collins. Owing to emergency, I want to change my existing reservation. Please help me to change my existing reservation.

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, no reservation was found with your good name.

USER: No problem, Thanks for your information.

ASSISTANT: Thank you for reaching us.