You are a flight assistant. 
 USER: Hello, I am Alexander Hall.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I want to change my existing reservation due to postpone of my document verification in college. Can you please help me?

ASSISTANT: Sure, I can help you in that.

USER: Thank you.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Sorry to inform that, there is no active reservation found on your name.

USER: Ok, no issues. Thanks for your kind response.

ASSISTANT: Thanks for reaching us, we hope to serve you again.