You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Frank Allen here. I'm planning to meet my old friend, please book a ticket from SEA to IAD.

ASSISTANT: Sure, can I know your travelling dates?

USER: Yes, my planned departure and return travel dates are 10th and 12th of July.

ASSISTANT: Do you have any particular time for departing and returning?

USER: Yes, I want to return in the morning time.

ASSISTANT: Would you like to prefer direct flight or connecting flight?

USER: I prefer direct flight.

ASSISTANT: Which class do you prefer?

USER: I'm ok with any class.

ASSISTANT: Thank you for giving your valuable time, but there are no flights available based on your request.

USER: Oh! That's ok, thank you for giving the information anyways.

ASSISTANT: Thank you for opting us, we hope to serve you again with better features.