You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you at this moment?

USER: I am looking to change my travel dates in my past ticket Can you please help me?

ASSISTANT: Sure, I will help you with that. Can you please provide your name to check your previous reservation?

USER: Thank you, I am Helen Roberts.

ASSISTANT: Ok, please be on hold to check. We regret to inform you that, there is no reservation on your name in our records.

USER: It's ok, thank you for your help.

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