You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Steven Moore.

ASSISTANT: How may I assist you today?

USER:  I want to book a flight ticket to Las Vegas-LAS to visit Golden Gate bridge, so help me to find a best flight.

ASSISTANT: Steven Moore, please provide your planned dates for this journey?

USER: My trip dates are 09/21 to 09/23.

ASSISTANT: May I know your origin airport code?

USER: My source is SFO.

ASSISTANT: There are no flights available currently for you. Sorry for the inconvenience.

USER: That's ok, thank you.

ASSISTANT: Thank you for choosing our services.