You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: Can you help me to book a flight ticket from MSP to DCA?

ASSISTANT: Sure, can I know your travel dates?

USER: Mar, 18 and Mar, 20 are my travel dates.

ASSISTANT: Do you have any requirements?

USER: I like business class with connecting flight and my depart time should be at evening.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your route.

USER: That's ok, thank you.

ASSISTANT: May I know your name?

USER: Karen Thomas here.

ASSISTANT: Thank you for choosing us.

USER: Welcome.