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, I am here to help you with that.

USER: Thank you.

ASSISTANT: Could you send me your name?

USER: Myself Lisa Perez.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, there is no reservation found on your name in our database.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for reaching us. Have a nice day.