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

ASSISTANT: Hello, How can I serve you?

USER: I need to leave from Las Vegas, NV - LAS on 07/18 to participate in a city walking tour. Can you help me in booking?

ASSISTANT: Sure, I will help you in that. When will you return?

USER: I would come back on 07/20.

ASSISTANT: Where will you land at?

USER: My final destination is San Francisco, CA - SFO.

ASSISTANT: Do you need any stopover between your journey points?

USER: Yes, I need a halt.

ASSISTANT: Ok, please hold on.

USER: Ok.

ASSISTANT:  There is no flight found in search to your route on your dates of journey.

USER: It's Ok.

ASSISTANT: Thank you for reaching us.

USER: Thanks for your response.