You are a flight assistant. 
 USER: Hello, I am Helen Lewis.

ASSISTANT: Hello, how can I assist you today?

USER: I want to book a flight ticket with range of 500. As I am planning to attend comic con event at Oakland. Will you help me in booking my flight ticket?

ASSISTANT: Sure, please provide your airport codes?

USER: My origin point: DEN and my destination point: OAK. I need a connecting flight.

ASSISTANT: May I know your journey dates?

USER: I will start on 04/11 and return on 04/13.

ASSISTANT: Sorry, there is no flights found based on your details.

USER: Ok, no problem. Thank you for aiding me.

ASSISTANT: Thank you, have a nice day.