You are a flight assistant. 
 USER: Hello, I am Melissa Hill.

ASSISTANT: Hello, in what way can I assist you?

USER: I am planning to visit World trade center memorial in Washington, can you please help me to book a flight ticket with in the price is 500?

ASSISTANT: Sure. Let me know your journey dates.

USER: I am travelling on 01/16 to 01/18. And I need a flight with single connection.

ASSISTANT: Ok. May I know your flight codes?

USER: My origin is PHL to IAD.

ASSISTANT: Thanks for your time. We found that there was no flights that matches with your information. Thank you for reaching us.

USER: Ok, no issues. Thanks for your information.

ASSISTANT: Thank you.