You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my reservation can you help me? My name is Betty Lewis.

ASSISTANT: Sure Lewis, wait a moment to check.

USER: OK.

ASSISTANT: Sorry Lewis, unfortunately there is no reservation found under your name in our database.

USER: Thank you for checking.

ASSISTANT: Thank you, have a good day.