You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Frank Davis, want to travel from DEN to HOU. Please help me in booking my ticket.

ASSISTANT: Sure, can I know your travel dates?

USER: Sure, my travelling dates are from 04/16 to 04/18.

ASSISTANT: Please give me a minute.

USER: Sure.

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

USER: Oh! It's ok, not an issue. Anyway, thank you for your help.

ASSISTANT: You are welcome.