You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I best serve you now?

USER: Please change my existing reservation.

ASSISTANT: Sure, I can change your reservation right now. Please provide your name so, that I can check your reservation and change it?

USER: I am Stephanie Martinez.

ASSISTANT: Give me a minute please.

USER: Sure.

ASSISTANT: Unfortunately, there is no reservation found on your name.

USER: Thank you.