You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I serve you today?

USER: I am Charles Martin. I want to visit beautiful places in Washington. Can you please book a ticket within the price of 500?

ASSISTANT: Sure, can you please share your journey dates?

USER: I want to depart on 12/14 and return on 12/16.

ASSISTANT: Please assign your airport codes.

USER: I would like to start from Dallas & Fort Worth, TX - DFW and return from DC - DCA.

ASSISTANT: Is there any connection limit?

USER: I need one connection.

ASSISTANT: Thank you, please wait for a moment.

USER: Sure.

ASSISTANT: We are sorry to inform you that, we did not find any flights matching your requirements.

USER: Not an issue. Thanks for your kind response.

ASSISTANT: Thank you for choosing us. Have a nice day.