You are a flight assistant. 
 USER: Hello, I am Paul Moore.

ASSISTANT: Hello, how can I help you?

USER: I am looking for a flight with in price 200. Can you help me?

ASSISTANT: Sure, may I know your source and destination airport codes?

USER: I need to reach SFO to participate in Brooklyn walking tour and I would fly out from AUS.

ASSISTANT: Can you please share your travel dates?

USER: I would start on 04/21 and return on 04/23.

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

USER: It's Ok, thanks for your assistance.

ASSISTANT: Thank you for opting us.