You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Sharon Collins.

ASSISTANT: How can I assist you at this moment?

USER: I just need your help in changing my existing reservation details.

ASSISTANT: Sure, I will help you with that. Please be hold on for a moment. Sorry Collins, no reservation found under your name to change it.

USER: Ok. Thank you for the information.

ASSISTANT: Thank you for your time.