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

ASSISTANT: Hello, how may I help you?

USER: Due to emergence, I want to change my existing reservation. Can you help me with it?

ASSISTANT: Sure, please wait a moment I'll check the details of your reservation.

USER: Ok.

ASSISTANT: Sorry to say, in my database I didn't found any details regarding your reservation.

USER: Thank you.

ASSISTANT: Thanks for reaching us. Have a nice day.