You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Justin Williams.

ASSISTANT: How may I help you out?

USER: Can you please find a flight which is an economy class from OAK to DEN?

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: Thank you. I am willing to travel on the dates of Sept 7th and 9th.

ASSISTANT: Do you have any specifications?

USER: I need a flight which is departing in the afternoon time.

ASSISTANT: Sorry, there are no flights found.

USER: It's ok, not a problem with that. Thank you for your time.

ASSISTANT: Thank you for reaching us.