You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Please help me to book a flight ticket in my preferable travel dates Dec, 10 and Dec, 12.

ASSISTANT: Sure, please help me with your connection limit.

USER: I would prefer single connection.

ASSISTANT: Ok, May I know your source and destination?

USER: DEN and SFO are my airport codes.

ASSISTANT: Ok, Do you have any class preference?

USER: No, thanks.

ASSISTANT: Ok, Is there any other preferences?

USER: I need to return at afternoon time.

ASSISTANT: Thank you for providing details, we did not find any flights with your given requirements.

USER: That's ok, thank you for the information.

ASSISTANT: Please provide your name for documentation purpose.

USER: Joseph Perez.

ASSISTANT: Thank you for opting us.