You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you at this moment?

USER: Please help me to book a flight ticket from DFW to IAH.

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Can I have your travelling dates please?

USER: My travelling dates are from Apr, 26 to Apr, 28.

ASSISTANT: Ok, please let me know the preference of class.

USER: I am comfortable with any class.

ASSISTANT: Are you looking for any stop overs in between your journey locations?

USER: Yes, I need a single connecting flight.

ASSISTANT: Do you prefer any specific airlines?

USER: I am ok with any airlines.

ASSISTANT: Can I have your good name please?

USER: I am Elizabeth Harris.

ASSISTANT: Sorry to inform you  that no flight is available to you on your dates.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us, have a good day.