You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I want to book a ticket from IAD to SFO.

ASSISTANT: Sure, I am happy to help you with that. May I know your travel dates please?

USER: Trip dates are from May, 3 to May, 5.

ASSISTANT: Let me know your connection limit.

USER: I need direct flight.

ASSISTANT: Do you have any class preference?

USER: I am comfortable with any class preference.

ASSISTANT: May I know your other specifications, if any?

USER: I prefer normal-cost airline.

ASSISTANT: Please, provide me your name.

USER: My name is Edward Anderson.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, we did not found any flights running on your desired routes.

USER: Thank you.

ASSISTANT: Thank you for reaching us.