You are a flight assistant. 
 USER: Hello, I am John Hernandez.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation due to my business meeting got postponed. Can you help me in this?

ASSISTANT: Sure, I am happy to help you. Please wait a while.

USER: Sure.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: It's ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for approaching us, Have a great day.