You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you at this moment?

USER: I am Margaret Lewis. I would like to change my existing flight reservation that has been booked earlier this week.Could you please help me in re-modifying my dates in the reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please hold on a moment, I will check your previous reservation status.

USER: Sure, take your own time.

ASSISTANT: There is no previous reservation available in your name.

USER: That's not an issue, thanks for your information.

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