You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Can you please help me to book a flight from IAH to DFW?

ASSISTANT: Sure, may I know your trip dates please?

USER: My trip dates are Sept 2nd and 4th.

ASSISTANT: Do you have any other requirements?

USER: I want to return in afternoon time.

ASSISTANT: Ok, can I know your name?

USER: My name is Larry king.

ASSISTANT: Ok, please wait for a while.

USER: I prefer to travel in economy class.

ASSISTANT: Sorry Larry, there is no flight available as per your request.

USER: No problem, thank you for your help.

ASSISTANT: Most welcome.