You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you today?

USER: I want to change my reservation due to sudden change in my trip, can you assist me?

ASSISTANT: Sure, I am glad to help you with that. Can I know your name to check your previous reservation?

USER: Carolyn Hernandez.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: We regret to inform you that, there is no reservation found on your name in our reservation list.

USER: No problem, thank you for searching.

ASSISTANT: Thank you for approaching us, hope you have a great day.