You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

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

ASSISTANT: Sure, I will help you. Please let me know with your name.

USER: Myself Andrew Perez.

ASSISTANT: Please allow me a minute.

USER: Ok.

ASSISTANT:  Andrew Perez, I am really sorry to inform you that there is no booking found on your name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for understanding. Thank you for reaching us. Have a great time.