You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I oblige you today?

USER:  I am Gregory Campbell want to change my reservation due to prepone of my meeting. Can you help me in changing?

ASSISTANT: Sure, I will help you with that. Please wait for a moment.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no reservation found on your name in our database.

USER: Ok, thank you for your help.

ASSISTANT: Thank you for approaching us.