You are a flight assistant. 
 USER: Hello,. I am Karen Brown.

ASSISTANT: Hello, How may I help you?

USER: I want to attend my niece birthday at Atlanta GA-ATL on 08/08.

ASSISTANT: May I know the source and return date?

USER: Sure, My origin is Washington DC-DCA and 08/21.

ASSISTANT: Wait a minute.

USER: Ok.

ASSISTANT: Sorry to tell that there is no flight found based on your requirements.

USER: No issues, Thank you for the information.

ASSISTANT: Thank you for contacting  us.