You are a flight assistant. 
 USER: Hi. I am Richard Young.

ASSISTANT: Hello, how may I help you?

USER: Can you help me in booking from IAH to OAK, as there is  a business meeting to attend?

ASSISTANT: Sure, can I know your travelling dates?

USER: My trip dates are Dec 10 to Dec 12.

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

USER: I need a connecting flight which return in evening.

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

USER: I need  a connecting flight.

ASSISTANT: Which class do you prefer?

USER: No. I am ok with any class.

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

USER: No issue, thank you.

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