You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: Can you aid me to book my ticket from OAK to DCA?

ASSISTANT: Sure, will you mention your travelling dates please?

USER: My trip dates are Dec 1 and Dec 3 respectively.

ASSISTANT: Do you have any preferences about flight connections?

USER: I  prefer for single connecting flight to travel.

ASSISTANT: Do you have any preferences about class?

USER: My return time should be in the evening.

ASSISTANT: Please mention your name.

USER: Kevin Carter here.

ASSISTANT: There is no flights found under your preferable details.

USER: Thanks for the help.

ASSISTANT: Welcome, have a great day.