You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my existing reservation, due to some work at my office.

ASSISTANT: Sure, may I know your name?

USER: Can you please help me for changing my reservation?

ASSISTANT: Ok, I will help you.

USER: I am David Jones.

ASSISTANT: Wait a minute.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found on your name.

USER: Ok, Thank you.

ASSISTANT: Thank you for choosing us.