You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you today?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, we are here to help you. Can you please provide me your name?

USER: My name is Katherine Clark.

ASSISTANT: Thank you for providing your name, Please stand by I will revert you.

USER: OK.

ASSISTANT: Thank you for waiting, I am sorry to say there was no reservation found by your name.

USER: OK, thanks for your information.

ASSISTANT: Have a nice day.