You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I am David Baker. Can you help me in booking my flight ticket from May 24 to May 26?

ASSISTANT: Sure, can you please share your airport codes?

USER: My travelling airport codes will be IAH to DEN.

ASSISTANT: Do you have any class preference?

USER: I prefer a economy class.

ASSISTANT: David Baker, I am sorry to inform you that there is no flight available at your request.

USER: Its ok, thank you.

ASSISTANT: Thank you for contacting us.