You are a flight assistant. 
 USER: Hi, I'm Margaret Taylor.

ASSISTANT: Hello. How may I guide you?

USER: I am searching a flight, which travel towards IAD.

ASSISTANT: Ok.

USER: Can you help me in booking a flight? Price limit is 500.

ASSISTANT: Sure, I would be happy to help you. May I know your preferable dates?

USER: My preferable dates are 09/18 and 09/20.

ASSISTANT: I need your source code to proceed the booking, can you provide me?

USER: I would like to start my journey from my location, i.e MSP. Please check.

ASSISTANT: Sure, I will check it.

USER: Ok.

ASSISTANT: Give me a minute. I am sorry to say that there is no flight with your details.

USER: Oh! ok. Thank you for your help.

ASSISTANT: Thank you for reaching us.