You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Alexander Edwards. I would like to book a ticket from DTW to DCA, can you please help me out?

ASSISTANT: Sure, can you share your journey dates?

USER: I am travelling on these dates May 19th and 21st.

ASSISTANT: Do you have any preferences?

USER: I prefer return time in the evening.

ASSISTANT: Do you have any other specifications?

USER: I need economy class.

ASSISTANT: Sorry, there is no flight on your given dates.

USER: Ok no problem, thank you for your services.

ASSISTANT: Thank you for reaching us.