You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: Can you please help me to book flight ticket from LAS to PHL?

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

USER: My trip dates are July 5 and July 7.

ASSISTANT: Do you have any other requirements?

USER: I prefer a connecting flight which depart in the evening.

ASSISTANT: Can I know your name please?

USER: Sure, I am Richard Johnson.

ASSISTANT: Sorry, we regret to inform you that there is no flight available as per your request.

USER: It's ok, thank you for searching.

ASSISTANT: Most welcome.