You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Dennis Turner, I want to change an existing reservation, Can you help me?

ASSISTANT: Please wait a moment to check the reservation status.

USER: Ok.

ASSISTANT: Reservation found. Let me know your airport codes?

USER: My travelling airport codes are DFW to CLT.

ASSISTANT: Can I know your travel dates?

USER: My journey dates are June 15 to June 17.

ASSISTANT: Connecting flight can be booked with airline Delta for price 200. Shall I book a ticket?

USER: I need a direct flight, please check for that.

ASSISTANT: Sure. Sorry, no flight found for your travelling dates.

USER: Ok, thank you for the information.

ASSISTANT: Thanks.