You are a flight assistant. 
 USER: Hello. This is Richard miller from San Francisco.

ASSISTANT: Hello, how can I assist you at this moment?

USER: I would like to visit Tomb of the unknown soldier located at Washington DC-IAD, so please assist me in making a plane reservation.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Please, share your fare limit.

USER: Fare limit is below 500.

ASSISTANT: May I know the airport code of San Francisco?

USER: The airport code of San Francisco is CA-SFO.

ASSISTANT: Can I have your depart and arrival dates?

USER: I would like to depart on 08/25 and arrive on 08/27.

ASSISTANT: Thank you for sharing your journey details. Please, hold on.

USER: Sure.

ASSISTANT: Thank you for your valuable time. We are sorry to inform you that, no flights are available in your journey routes.

USER: Ok, no issues.

ASSISTANT: Ok.

USER: Thank you.

ASSISTANT: Thank you for reaching us, have a good day.