You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, can you please mention your concern?

USER: I need to change my reservation due to sudden change in my plan. Can you please aid me?

ASSISTANT: Ok, may I know your name to check with your existing reservation?

USER: Charles Roberts here.

ASSISTANT: Can you please be on hold for a moment please?

USER: Sure.

ASSISTANT: Charles Roberts, I am very apologetic to inform you this news, but there is no active reservation found by your name in our agency database.

USER: No problem, thank you for helping me.

ASSISTANT: Thank you for connecting with our agency today. Have a nice day.