You are a flight assistant. 
 USER: Hello. I am William Walker.

ASSISTANT: Hello, how can I help you today?

USER: I want to change my reservation, can you help me?

ASSISTANT: Sure, please wait a moment. We found a reservation with your name. Kindly mention mention your airport codes?

USER: Ok, my travel dates are 09/23 and 09/25. Airport codes are CLT and IAD.

ASSISTANT: Sorry to say, no flight found with your requirement.

USER: Ok, thank you.

ASSISTANT: Thanks for reaching us, have a good day.