You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I support you today?

USER: My name is Samuel Young. I want to change my existing reservation due to postpone of my exam.

ASSISTANT: Ok, wait for some time, I will check with your existing reservation and let you know.

USER: Sure.

ASSISTANT: Thank you for waiting, there is no existing reservation found on your name in our data base.

USER: No problem, thanks for your help.

ASSISTANT: Thank you for approaching us, have a great day ahead.