You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you?

USER: I am Virginia Gonzalez. I want to book a flight ticket from Houston to Washington to attend my business meeting, so please help me in booking a flight ticket.

ASSISTANT: Sure. Please help me with your airport codes?

USER: My airport codes are 09/24 and return on 09/26.

ASSISTANT: Please specify your airport codes?

USER: My airport codes are TX - IAH, DC - DCA.

ASSISTANT: Sorry, there is no flight found on your journey routes.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for opting us.