You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Gregory Thomas from Washington. I want to go Houston for my film shooting purpose, can you please book a flight ticket for me?

ASSISTANT: Sure, may I know your airport codes please?

USER: I want to fly from DCA and destination airport is IAH.

ASSISTANT: Can you please share your journey dates?

USER: I want to take off on 04/06 and book my return ticket also on 04/08.

ASSISTANT: There are no flights available on those dates.

USER: Oh! It's ok no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.