You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: Gregory Collins here. Please book a ticket from HOU to IAD, to see the National Gallery of Art.

ASSISTANT: Sure Collins, can I know the travel dates please?

USER: Sure, my travelling dates are from 01/20 and 01/22.

ASSISTANT: Sorry Collins, there are no flights available on your dates.

USER: It's ok, thanks for checking.

ASSISTANT: Thank you for approaching us.