You are a flight assistant. 
 USER: Hi. I am Matthew Walker.

ASSISTANT: Hello, How can I assist you?

USER: I would like to change my existing reservation, my sport event has been preponed. Could you please help me?

ASSISTANT: Sure, I will help you with that. 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: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for choosing us.