You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: My name is John Young. I want to do some changes in my existing reservation, can you help me for that?

ASSISTANT: Yes, please I will help you with the change of flight ticket booking. Please wait for a moment.

USER: Thank you. Sure, I will wait for your response.

ASSISTANT: Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it.

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

ASSISTANT: Thank you.

USER: Welcome.