You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you now?

USER: I am Eric Williams, want to travel from SFO to DCA. Please help me in booking my ticket.

ASSISTANT: Sure, I am oblige to help you with that. Can you please provide your preferable departure and return dates of travelling?

USER: Thank you and my travelling dates are from 12/16 to 12/18.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: At what time are you planning to depart and return?

USER: I am looking for normal cost airline and my return time should be in the evening.

ASSISTANT: Do you have any connection limit?

USER: I need a single connected flight.

ASSISTANT: Please be on hold to check the flights on your route.

USER: Sure.

ASSISTANT: We regret to inform you that, there are no flights available for your journey with your required preferences.

USER: It's ok, thank you for your help.

ASSISTANT: Thank you for reaching us, have a great day.