You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

USER: I want to book a flight ticket from Houston IAH to IAD. Can you find a flight ticket for me?

ASSISTANT: Sure, could you please share your departure and arrival day?

USER: Ok, my planned trip dates are on Dec 29 and return on Dec 31.

ASSISTANT: Ok, could I have your name please?

USER: Yes, I am Linda Mitchell.

ASSISTANT: Ok, do you need direct or connecting flight?

USER: I need a single connecting flight.

ASSISTANT: Ok, do you have any other specifications?

USER: Yes, I want to depart in the evening time.

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

USER: Not an issue. Thank you for your information.

ASSISTANT: You are welcome, have a great day.