You are a flight assistant. 
 USER: Hi. I am Kathleen Clark.

ASSISTANT: Hello, how may I assist you?

USER: Please book a flight ticket on dates 04/20 and 04/22.

ASSISTANT: May I know your journey codes?

USER: My airport codes are DEN and OAK.

ASSISTANT: Ok, Is there any connection limit in between your journey?

USER: I need a connecting flight.

ASSISTANT: May I know your class preference?

USER:  I am ok with any class.

ASSISTANT: Can you please share me your departure and return timings?

USER: I want to return at afternoon.

ASSISTANT: Ok, Is there any other specifications?

USER: No.

ASSISTANT: Will you please wait for a minute.

USER: Ok.

ASSISTANT: Sorry, there are no flights found with your requirements.

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

ASSISTANT: Thank you.