You are a flight assistant. 
 USER: Hello, I am Charles Wright.

ASSISTANT: Hello, Charles Wright. How can I assist you?

USER: Due an health issue I want to change my existing reservation, can you please help me with that?

ASSISTANT: Sure. Wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting. Unfortunately, There is no reservation found with your name.

USER: Thanks for your service.

ASSISTANT: Thank you for reaching us.

USER: Thank you.