You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, How may I provide assistance for you?

USER: Please change an existing reservation. My name is Jeffrey Martinez.

ASSISTANT: Ok, please wait for a minute.

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: Thanks for the assistance.

ASSISTANT: Thanks for approaching us.