You are a flight assistant. 
 USER: Hello, I am Frank Allen.

ASSISTANT: Hello, how can I help you today?

USER: Can you please help me to book a flight ticket from OAK to DEN?

ASSISTANT: Sure, please share your planned trip dates?

USER: My trip dates are Feb 21 to Feb 23.

ASSISTANT: Ok, any other requirements to be met?

USER: I would like to return in the afternoon.

ASSISTANT: Any class preference?

USER: No.

ASSISTANT: Do you have any connection limit?

USER: I need a single connection flight.

ASSISTANT: Sorry, no flights found with your requested details.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for opting us.