You are a flight assistant. 
 USER: Hello, I am James Williams.

ASSISTANT: Hello, how may I be at your service today?

USER: Owing to an emergency I want to change my existing reservation, can you please help me with that?

ASSISTANT: Sure. we are glad to help you. Can you please wait for a while, I will check  your reservation and revert to you.

USER: Sure.

ASSISTANT: Thank you for waiting. We are sorry to inform you that, we did not find any reservation with your name.

USER: Ok, no issues, thanks for your information.

ASSISTANT: Thank you for reaching us. Have a good day.