You are a flight assistant. 
 USER: Hello, I am Christine Smith.

ASSISTANT: Hello, how can I help you?

USER: I want to travel to Houston TX-HOU on 12/15 to enjoy snow storms at my grandmother house. Could you please help me in booking a flight ticket from Denver, CO-DEN and return on 12/17?

ASSISTANT: Ok sure, just let me check the flight availability.

USER: Ok.

ASSISTANT: I am very sorry to inform you that there is no flight available during your visiting time. Sorry for the inconvenience. Hope to serve you better next time.

USER: No problem, Thank you for the information.