You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Can you help me to book a flight ticket from ATL to SFO?

ASSISTANT: Sure, when are you planning to travel?

USER: My travel dates are Apr 19 and Apr 21.

ASSISTANT: May I know your name please?

USER: I am Dennis Davis.

ASSISTANT: Do you have any preferences?

USER: I would like to depart and arrival in the evening time.

ASSISTANT: Sorry, no flights were available at this moment in your desired routes.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.