You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am George Green. I want to do some modifications in my previous reservation, can you please help me.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Yes, I found your previous reservation to modify, can you please provide me your travelling dates?

USER: Sure, my new travelling dates are from 09/28 till 09/30.

ASSISTANT: Ok, may I know your airport codes?

USER: I want to fly from DFW to DTW.

ASSISTANT: Sorry, no flight is available on your route.

USER: That's ok, thank you for your information.

ASSISTANT: Welcome, have a nice day. Thank you for connecting us.