You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change existing reservation due to postpone of my exams. Can you help me in that?

ASSISTANT: Sure, may I know your name for the changing process?

USER: Joshua Robinson here.

ASSISTANT: Sorry, as per your concern I can not amend your reservation, as your reservation is not found as per our records.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Welcome, thank you for reaching us.