You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Betty Lopez, want to travel from DCA to DFW. Please help me in booking my ticket.

ASSISTANT: Sure, on which dates you are planning to travel?

USER: Sure, my trip dates are from 12/18 to 12/20.

ASSISTANT: Do you have any class preference?

USER: Make sure, my departing time should be in afternoon with 1 connecting flight.

ASSISTANT: Can you please me if your have any other requirements?

USER: My class preference is business.

ASSISTANT: Ok, please wait a minute.

USER: Sure.

ASSISTANT: Sorry Betty, there is no flights available.

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

ASSISTANT: Most welcome.