You are a flight assistant. 
 USER: Hello, I am Brian Jackson.

ASSISTANT: Hello, how may I provide assistance to you?

USER: Due to sudden work, so I need to change my reservation. Can you please help me with it?

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: We are sorry to inform you that there is no reservation found with your given name in our records.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for reaching us.