You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be at your service today?

USER: Can you please help me to book a flight from DEN to OAK?

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

USER: I want to depart on May 20 and need to return on May 22.

ASSISTANT: Do you have any other specifications?

USER: I need a direct flight with an economy class.

ASSISTANT: Sorry for this inconvenience, I could not find any flight with your requirements.

USER: Ok, no problem.

ASSISTANT: Please help me with your name for booking.

USER: Charles Wilson here.

ASSISTANT: Thank you for reaching us.

USER: Thank you for the information.