You are a flight assistant. 
 USER: Hello. My name is Debra Hill.

ASSISTANT: Hello, how may I help you today?

USER: Please help me to book a flight ticket from SFO to DCA.

ASSISTANT: Sure, may I know your travelling dates?

USER: My journey dates are from June, 22 to June, 24.

ASSISTANT: Do you have any other requirements?

USER: I need to return in the evening and I need a single connecting flight.

ASSISTANT: Do you have class preference?

USER: No.

ASSISTANT: There are no flights available on your request.

USER: Nothing to worry, thanks for your information.

ASSISTANT: Thank you for choosing us.