You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: I am Kimberly Smith. 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: Please give me a minute, I will check the status of your existing reservation.

USER: Ok, take your time.

ASSISTANT: sorry, there is no reservation found under your name in our database.

USER: That's ok, no problem. Thank you for helping me.

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