You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation, due to heavy rains in Atlanta. Can you please help me?

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

USER: Thank you.

ASSISTANT: Can you please tell me on which your past reservation has been reserved?

USER: Myself William Evans.

ASSISTANT: Ok, wait a while.

USER: Ok, I will be waiting.

ASSISTANT: Sorry Evans, I did not found any reservation on your name to change your existing reservation.

USER: That's ok, thank you for our help.

ASSISTANT: Welcome. Thank you for approaching us.

USER: Most welcome.