You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: Jack Lewis here. I am planning to book a flight ticket from DTW to DCA, can you help me?

ASSISTANT: Sure, I will help you. Can you provide your preferable dates of journey?

USER: My travelling dates are from 08/21 to 08/23.

ASSISTANT: Sorry to say this, from our service there is no flight to such a destination.

USER: It's ok. Thank you.

ASSISTANT: Thank you for contacting our service.