You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I would like to change my existing reservation, can you help me in that?

ASSISTANT: Sure, I am here to help you with that, can I know your good name to proceed further?

USER: Sure, myself Daniel Moore.

ASSISTANT:  I am very sorry to inform you that there is no reservation found under your name in our database.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for reaching us.