You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, may I know your name?

USER: I am Joseph Robinson.

ASSISTANT:  Joseph Robinson, tell me how may I help you?

USER: I am planning for a trip with my friends to IAH.Can you please help me to book a flight ticket from IAD?

ASSISTANT: Sure, may I know your travelling dates?

USER: I prefer to travel on 09/07 and 09/09.

ASSISTANT: There is a flight available with us with your provided information from Southwest airline, and the fare is 1000. Is it ok for you?

USER: But I need a flight ticket with price 500.

ASSISTANT: Oh! I am sorry, there is no flight available with the price 500.

USER: That's ok. Thank you for your information.

ASSISTANT: Most welcome.