You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: Can you please help me to book flight ticket from IAD to SFO?

ASSISTANT: Sure, can you please share me your travelling dates?

USER: My trip dates are June 17 and June 19.

ASSISTANT: Do you have any connection limit?

USER: I prefer a direct flight.

ASSISTANT: Is there any other specifications in your journey?

USER: I prefer an economy class for this trip.

ASSISTANT: May I know your name?

USER: I am Michelle Johnson.

ASSISTANT: Sorry, there were no flights with your given details.

USER: It's ok, thank you.

ASSISTANT: Thank you for reaching us.