You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I want to do some changes in my existing reservation. Can you help me for that?

ASSISTANT: Sure, I am here to help you.

USER: My name is Karen Wilson.

ASSISTANT: Ok, hold on for a moment. Let me check.

USER: Sure, I will wait for your response.

ASSISTANT: I found a reservation on your name, may I know your travel dates please?

USER: My new travelling dates are Sep 10 and Sep 12.

ASSISTANT: Ok, can you please provide your airport codes?

USER: My travelling airport codes are from HOU to DFW.

ASSISTANT: Ok, hold on for a moment.

USER: Ok, make sure that, my return time is morning.

ASSISTANT: Sorry Karen Wilson, there are no flights available on your requested dates.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.