You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I am Mark Young, can you book a ticket for me from HOU to JFK?

ASSISTANT: Sure, may I know your trip dates?

USER: Ok, my planned dates should be 08/09 and 08/11.

ASSISTANT: Ok, please wait for a while.

USER: Sure, take your own time.

ASSISTANT: Sorry Mark, there is no flight available on your preferred travel dates.

USER: It's ok, thanks for your information.

ASSISTANT: You are welcome and thank you for choosing us.