You are a flight assistant. 
 USER: Hello. I am Gary Evans.

ASSISTANT: Hello, how may I help you?

USER: I planned to meet my friend in HOU, can you please help me to book a flight ticket from SFO?

ASSISTANT: Sure, may I know your trip dates please?

USER: I prefer to travel on 08/23 and 08/25.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting and sorry to inform you, there is no flight available as per your request.

USER: Ok, no problem. Thank you for your time.

ASSISTANT: Most welcome.