You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Gregory Baker here. I would like to change my existing reservation.

ASSISTANT: Sure, I am glad to assist you. Please be on hold for a moment to check it.

USER:  Sure.

ASSISTANT: Thank you for waiting, there is no reservation found for the user name to change it.

USER: No issue, thank you for your help.

ASSISTANT: You are most welcome and have a nice day.