You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

USER: My name is Stephen Mitchell. I would like to change an existing reservation.

ASSISTANT: Sure, I am here to help you for this. Let me check your reservation status in our database.

USER: Sure.

ASSISTANT: Sorry for inconvenience, no reservation is found with your criteria.

USER: No problem. Thank you for the information.

ASSISTANT: Thank you very much for approaching our agency.