You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you at this moment?

USER: My name is Raymond Allen as there is a music concert in Oakland which I planned to attend. Can you book a flight ticket from DCA to OAK?

ASSISTANT: Sure, I will help you. Please send your travelling dates.

USER: Ok, please book a flight ticket on the dates 11/25 and 11/27 respectively.

ASSISTANT: Please wait for a moment. In meanwhile please mention the specifications you need in your journey.

USER: Yes, I need a connecting flight for my trip?

ASSISTANT: Sorry to say this, there is no flight available on your requested dates with your requirements.

USER: Ok, I will book a flight ticket through other source. Thank you for assisting me.

ASSISTANT: You are welcome, have a nice day.