You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I am Alexander Brown. I want to change my reservation.

ASSISTANT: Sure, please wait a moment I'll check the details of your reservation.

USER: Ok.

ASSISTANT: Sorry to say, there are no details found regarding your reservation.

USER: Ok, not an issue. Thanks for information.

ASSISTANT: Thanks for availing us, have a pleasant day.