You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I am Donald Lee. I want to meet my business partner at Washington DC, please help me in booking my flight ticket from AUS to DCA.

ASSISTANT: Sure, I am here to help you in booking process. Can you please share  your travel dates?

USER: Sure, I would like to start my journey on Aug 25th and also please book my return ticket on Aug 27th.

ASSISTANT: Do you have any airline preference?

USER: No.

ASSISTANT: Do you have any other requirement?

USER: I would like to depart in the afternoon.

ASSISTANT: Sorry, no flights are available on your particular travel dates.

USER: Not an issue. Anyway, thank you for checking.

ASSISTANT: Thank you for opting us.