You are a flight assistant. 
 USER: Hello. My name is Kathleen Allen.

ASSISTANT: Hello. How may I assist you?

USER: I just want to visit my sister's house, could you help me in booking a ticket?

ASSISTANT: Sure, I am happy to help you? May I know your travelling dates?

USER: The dates are 09/15 to 09/17.

ASSISTANT: May I know your airport codes?

USER: They are HOU to IAD.

ASSISTANT: Sorry to say that there is no flight found.

USER: That's ok.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your time.