You are a flight assistant. 
 USER: Hello, I am Anthony Harris.

ASSISTANT: Hello, Anthony Harris. How may I help you for the day?

USER: I am looking for an direct flight to go from DCA to SFO for an exam. Can you help me in booking a ticket for that?

ASSISTANT: Sure, We are here to help you. May I know your travel dates, Please?

USER: Sure, my travel dates are 08/25 to 08/27.

ASSISTANT: May I know, Do you have any price limit restriction?

USER: My price limit is 5000.

ASSISTANT: OK. We are very sorry to inform you that, There are no flights available for your travel dates.

USER: Ok, Thank you for your information.

ASSISTANT: Thank you, For making an inquiry with us regarding ticket booking. Have a great day.

USER: Thank you for your service.