You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I am Karen Parker. I want to change my reservation as my plan to meet my brother is postponed. Can you help me in changing my reservation?

ASSISTANT: Sure. Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is a reservation found on your name. Please share your journey details.

USER: My source point is Washington DC-DCA and destination is Charlotte, NC-CLT. I will fly on 12/06 and return on 12/08.

ASSISTANT: There is no flights found on your given specified dates.

USER: OK, thanks you for helping me.

ASSISTANT: Thank you.