You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can I assist you at this moment?

USER: I'm Brandon Collins. I am planning to attend music concert at San Francisco, can you please help me with booking a flight ticket?

ASSISTANT: Yes, I will help you about it. Can you please provide your location points in detail?

USER: My source airport code is DCA and the destination airport code is SFO.

ASSISTANT: Ok, please help me with your preferable dates of journey.

USER: Sure, I would like to take off on 07/30 and return back on 08/01.

ASSISTANT: Sorry Collins, there is no flight which can travel to your specified destination on your planned dates.

USER: Ok, no issues. Thank you for checking.

ASSISTANT: Most welcome, thank you for opting our service.

USER: You are welcome.