You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Robert Brown.

ASSISTANT: How may I help you today?

USER: I would like to book a flight from DTW to IAD, can you please help me to book a flight ticket?

ASSISTANT: Robert Brown, please mention your travelling dates?

USER: Sure, my travelling dates are Dec 24 and Dec 26.

ASSISTANT: Please wait a moment.

USER: Sure, take your own time.

ASSISTANT: Sorry, there are no flight tickets available on your journey dates.

USER: That's ok, thank you for your information.

ASSISTANT: Thank you for reaching our service.