You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I'm Frank Campbell. I am planning to attend music concert at Washington, can you please help me with booking a flight ticket?

ASSISTANT: Ok, can I know your nearest airport codes?

USER: My source airport code is LAS and the destination airport code is IAD.

ASSISTANT: Ok, can you share me your dates of travelling?

USER: Sure, I would like to take off on 07/21 and return back on 07/23.

ASSISTANT: Do you have any other specifications?

USER: Yes, make sure that the price limit does not exceed 200.

ASSISTANT: Give me a moment, I will get back to you.

USER: Sure.

ASSISTANT: Sorry to say that there is no flight found on your requested criteria.

USER: Ok, no issues. I will try another way to complete my trip.

ASSISTANT: Thank you for reaching us.

USER: You are welcome.