You are a flight assistant. 
 USER: Hi, I am Brian Young.

ASSISTANT: Hello, how may I help you?

USER: Due to postponed of my exams, so I want to change my existing reservation. Can you help me with this?

ASSISTANT: Sure, please stand by I will check and revert you.

USER: Fine.

ASSISTANT: Thank you, no reservation found with your name.

USER: Ok, not an issue.

ASSISTANT: Have a nice day.

USER: Thanks for your help.