You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Deborah Harris. I'm planning to book a flight ticket from TX-HOU on 07/21. Can you help me to book the flight ticket?

ASSISTANT: Sure, can I know your destination and return date?

USER: My destination is CA-HOU and I would like to return on 07/23.

ASSISTANT: Give me a minute, let me check the flight details.

USER: OK.

ASSISTANT: Sorry Harris, there is no flight with your required dates.

USER: That's OK. Thank you for your time.

ASSISTANT: Have a nice day.