You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I am Elizabeth Miller. I would like to travel to Washington due to some business work. Can you please help me to book a flight ticket from Houston?

ASSISTANT: Sure, can you please mention with your dates of journey?

USER: Thank you. My dates of journey are Aug 1st and Aug 3rd.

ASSISTANT: Ok, may I know your respective airports codes please?

USER: The origin and destination airport codes are HOU and DCA.

ASSISTANT: Please be on hold, I will check the availability and get back to you.

USER: Ok, I will wait for your reply. Please make sure that the class should be an economy class flight.

ASSISTANT: Sure, I will wait.

USER: Sure.

ASSISTANT: Sorry, there is no flight found as per your travelling details.

USER: It's ok, not a problem with that. Anyways thank you for your help.

ASSISTANT: You are welcome.