You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you for the day?

USER: Please help me to book a flight ticket from SFO to DEN.

ASSISTANT: When you are wiling to travel?

USER: I want to fly on 20 Aug and return on 22 Aug.

ASSISTANT: Do you have any connection limit?

USER: I am ok with any connection limit.

ASSISTANT: May, I know your good name?

USER: Brandon Brown.

ASSISTANT: Sorry, we found no flights on your given dates.

USER: Oh! that very sad to hear, thank you.

ASSISTANT: Thank you.