You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I am Raymond Lewis. I want to change my existing reservation which I have done with my name 2 months back to attend a business meeting.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Sorry, there is no reservation is showing in our data base to change your reservation./.

USER: Ok, it may be not booked properly while booking itself. Thanks for your information.

ASSISTANT: Welcome. Have a nice day.