You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Sure, may I know your name to check for the previous reservation?

USER: Myself Edward Smith.

ASSISTANT: Please allow me a moment.

USER: Ok.

ASSISTANT: There is no reservation found under your name in our data base.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for contacting us.