You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I support you?

USER: I want to change my reservation due to sudden change in my trip. Can you assist me?

ASSISTANT: Sure, please provide me your name to check the status and revert you.

USER: Dennis Lee.

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT: Thank you for waiting, I regret to inform you that there is no reservation obtained on your name in our data base.

USER: No problem, thank you for searching.

ASSISTANT: Thank you for approaching us.