You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation.

ASSISTANT: Sure, can I know your name?

USER: Sure, my name is Dennis Allen.

ASSISTANT: OK Dennis, give me a moment.

USER: OK.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: It's OK. Thank you for your response.

ASSISTANT: Thank you for reaching us.