You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation, can you please help me with this?

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

USER: I am David Lewis.

ASSISTANT: Thank you very much. Please wait for a while, let me check your reservation status in our database.

USER: Sure.

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

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for reaching us.