You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

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

ASSISTANT: How can I assist you today? Ok, I will help you with changing the reservation.

USER: Thank you.

ASSISTANT: Please provide your name for checking the reservation status.

USER: I am Mark Lopez.

ASSISTANT: There is no reservation found under your name.

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

ASSISTANT: Welcome, have a great day.