You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I am Mark Clark, planning to visit Houston, TX - IAH to enjoy there with my childhood friends after a long time. Can you assist me to book a flight ticket from Dallas, TX - DFW?

ASSISTANT: Sure, can I know the trip dates please?

USER: My trip start from DFW on 11/26. And, my return to DFW on 11/28.

ASSISTANT: May I know your name for proceeding further?

USER: Myself Mark Clark.

ASSISTANT: Sorry Clark, there are no flights as per your request.

USER: It's ok fine.Thank you for the information.

ASSISTANT: You are welcome.