You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I have planned for the trip to Dallas to enjoy in the coming holiday, can you book a flight ticket from Oakland?

ASSISTANT: Sure, may I know your planned travel dates please?

USER: Sure, my planned trip dates are on Apr 21 and return on Apr 23.

ASSISTANT: Would you like to travel in a connecting flight or a direct flight?

USER: Ok, I need a single connecting flight.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: Do you have any particular time for departing and returning?

USER: Yes, I want to return in the morning.

ASSISTANT: May I know your good name please?

USER: Ok, my name is Gregory Mitchell.

ASSISTANT: Sorry, there is no flight available on your requested dates.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: You are welcome.