You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: Paul Evans here. Can you help me to book a connecting flight from DEN to SFO?

ASSISTANT: Sure, can you please share your travel dates?

USER: I want to fly on 10 May and return on 12 May.

ASSISTANT: Do you have any class preference?

USER: I prefer to travel in economy class.

ASSISTANT: May I know your connection limit?

USER: I need a connecting flight.

ASSISTANT: Do you have any other specification that you are looking for?

USER: My return time should be in the evening.

ASSISTANT: Paul Evans, I am sorry to inform you that there is no flight available at your request.

USER: It's ok, not a problem, thank you.

ASSISTANT: You are welcome. Thank you for reaching us.