You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: John Parker is my name.

ASSISTANT: How can I serve you?

USER: I want to change my existing reservation for my health checkup in Atlanta, can you help me?

ASSISTANT: Sure. Please wait a  while.

USER: Thank you for your positive response. Ok, I will be waiting for your reply.

ASSISTANT: Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: Oh! That's very disappointing to hear from your side. Anyways, thank you for checking.

ASSISTANT: Thank you for opting us.

USER: Most welcome.