You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I am Margaret Allen want to visit DFW, can you book a ticket from DCA?

ASSISTANT: Sure Allen, please provide me your travelling dates.

USER: Sure, my travelling dates will be 10/16 and 10/18.

ASSISTANT: Please wait for a minute, let me check.

USER: Ok.

ASSISTANT: Thanks for your waiting, I could not find any flight with your travelling dates.

USER: That's ok, thank you.

ASSISTANT: Thanks for choosing us, have a nice day ahead.