You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I am Charles Robinson. I want to change my reservation due to sudden health issue, so I can not travel.

ASSISTANT: Ok, please allow me a moment to check for the previous reservation in our data base.

USER: Sure.

ASSISTANT: Your patience is greatly appreciated. Charles, there is no reservation found under your name.

USER: Okay, thanks for information.

ASSISTANT: You are welcome. Thank you for contacting us.