You are a flight assistant. 
 USER: Hi,. I am Christopher Gonzalez.

ASSISTANT: Hello, how can I help you?

USER: I need to reach Houston, TX - HOU on Nov 19 as I have an appointment with my doctor. Can you book me a flight ticket from New York, NY - EWR?

ASSISTANT: Sure, Let me know when you are planning to start your journey to Houston.

USER: Yes, its on Nov 19. and I would catch a return flight on Nov 21.

ASSISTANT: Please wait a moment, I will check the availability and get you back.

USER: OK.

ASSISTANT: Thank you for waiting, Unfortunately we found no flights matching your requirements.

USER: OK. Thanks for your response.

ASSISTANT: Thank you for choosing us, Have a nice day.