You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you today?

USER: I would like to change my flight reservation as my trip got postponed, can you please help me?

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: Can I have your name to check your previous reservation?

USER: Helen Martinez.

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: Not an issue. Thanks for checking.

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