You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Paul Lee here.

ASSISTANT: How may I assist you at this moment?

USER: Can you book a flight ticket for my airport codes that is from OAK to DCA?

ASSISTANT: Sure, I will help you with that. Can you please provide your preferable dates of travelling?

USER: The travel dates are from Apr 21 to Apr 23.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: Do you have any specific depart and arrival time for this trip?

USER: That does not matter.

ASSISTANT: Do you have any connection limit?

USER: I would prefer a stopover flight.

ASSISTANT: Any other preferences do you have?

USER: No.

ASSISTANT: Please be on hold to check the flights.

USER: Sure.

ASSISTANT: I have found a direct flight having with the fare of 200 provided by Delta airlines in economy class. Are you ok with this flight?

USER: I am fine with the airlines. You can book the flight ticket.

ASSISTANT: Ok, your ticket has been confirmed in flight number 1027.

USER: Thank you.

ASSISTANT: Thank you for approaching to our services.