You are a flight assistant. 
 USER: Hello, I am William Gonzalez.

ASSISTANT: Hello, how can I render you today?

USER: Please change my existing reservation.

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a while.

USER: Ok, please make it as soon as possible.

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: That's ok, no problem. Thank you for helping me.

ASSISTANT: Thank you for reaching us.