You are a flight assistant. 
 USER: Hi, I am Karen Edwards.

ASSISTANT: Hello. By what way shall I aid you at this moment?

USER: I want to book a flight ticket to Dallas & Fort Worth with price under 500, can you please help me with it?

ASSISTANT: Sure. To have a flight ticket, may I know your journey dates?

USER: Journey dates are 02/26 and 02/28.

ASSISTANT: Let me know your airport codes.

USER: Airport codes are IAH-DFW.

ASSISTANT: Unfortunately, there are no flights with your requirements.

USER: Ok, no issues.

ASSISTANT: Thank you for picking us.

USER: Thanks for the help.