You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: Charles Rodriguez here. I want to travel from BOS to DCA for attending a business meeting. Can you please help me for booking the flight ticket?

ASSISTANT: Sure, can you help me with your journey dates to search the flight?

USER: My departure date is 12/20 and return date is 12/22.

ASSISTANT: Please wait for a moment.

USER: Ok, I will wait.

ASSISTANT: Sorry, there is no flight is available for you.

USER: So sad for that. Thank you for the information.

ASSISTANT: Thank you for choosing us, have a nice day.