You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I amend you?

USER: My name is Andrew Johnson, I want to change my existing reservation due to postpone of interview.

ASSISTANT: Sure, please be on hold.

USER: Ok.

ASSISTANT: Sorry, we did not find any reservation in your name.

USER: No problem, thank you for your service.

ASSISTANT: Thank you for choosing us.