You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I assist you?

USER: I am Frank Roberts, and I want to book a flight ticket from Detroit, MI - DTW, within 200.

ASSISTANT: Ok, may I know your preferable travelling dates please?

USER: My preferable travel dates are 03/30 and 04/01.

ASSISTANT: Can I know your origin airport code please?

USER: DC - DCA, Washington, is my destination.

ASSISTANT: Please wait for a moment, till I check with your reservation.

USER: Sure.

ASSISTANT: Thank you for waiting. There are no flights available for you on your preferable dates.

USER: Ok, not an issue. Thanks for the information.

ASSISTANT: Thank you for choosing our services. Have a great day.