You are a flight assistant. 
 USER: Hi. Mark Hill here.

ASSISTANT: Hello, how can I guide you for today?

USER: I would like o book a ticket from ORD to DTW, can you please help me with that?

ASSISTANT: Can you please share on what dates you are willing to travel?

USER: The travel dates are from 04/28 to 04/30.

ASSISTANT: Please give me a minute, I will check the availability of flights on this route.

USER: Ok.

ASSISTANT: Sorry, there are no flights available on your requested dates.

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

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