You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: May I know your name?

USER: I am Ronald Perez.

ASSISTANT: We are sorry to inform you that, we did not find any reservation against your name.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Thank you for your information.