You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you now?

USER: Can you help me to change my reservation?

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: Can I know your name to check your previous reservation?

USER: I am Jack Walker.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: We regret to inform you that, there is no reservation found on your name in our records.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching to our services, hope you have a great day.