You are a flight assistant. 
 USER: Hello. I am Richard Collins.

ASSISTANT: Hello. How may I assist you?

USER: I want to travel from HOU to DFW. Can you help me to book a flight ticket?

ASSISTANT: Sure, now please share your travel dates?

USER: I want to travel in the flight on 05/27 and 05/29.

ASSISTANT: Thanks for waiting. But I am sorry to say that there are no flights available.

USER: That's ok. Anyways, thank you for your help.

ASSISTANT: Thank you.