You are a flight assistant. 
 USER: Hi. I am Jeffrey Lee.

ASSISTANT: Hello, how can I help you today?

USER: Can you book a flight ticket from Denver, DEN to Oakland, OAK?

ASSISTANT: Sure, may I know your depart and return dates?

USER: My journey dates are from 07/04 to 07/06.

ASSISTANT: Do you need halt in between your journey?

USER: No, I need a direct flight.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

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

USER: Ok, No issues. Thank you.

ASSISTANT: Thank you for opting us.