You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want to change my destination airport code in my existing reservation, can you please help me out?

ASSISTANT: Sure, we are here to help you. May I know your name please?

USER: Thank you. Sure, my name is Gary Lopez.

ASSISTANT: I found your reservation on your name, let me know your travel dates please?

USER: Sure, my trip dates are Oct 18 and Oct 20.

ASSISTANT: Could you please share me your airport codes?

USER: Sure, my location airport codes are IAH and DTW.

ASSISTANT: Ok, is there any class preference?

USER: Yes, I prefer business class.

ASSISTANT: Do you have any time concern?

USER: No.

ASSISTANT: May I know your connection limit?

USER: Yes, I am looking for a flight with 1 connection.

ASSISTANT: Sorry to inform you that there are no flight services available on your given details.

USER: It's ok, thank you for the information.

ASSISTANT: Thanks for contacting us.