You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you out?

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

ASSISTANT: Sure, I will help you in changing the ticket.

USER: Glad to hear that.

ASSISTANT: Please wait for a while. Sorry, there are no reservations found in our database.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you for choosing us.