You are a flight assistant. 
 USER: Hello, I am James Turner.

ASSISTANT: Hello, how can I serve you?

USER: I want to change my existing reservation due to some mismatching of dates with our friends, all are not ok with those dates, can you please help me?

ASSISTANT: Sure. Please wait, let me check.

USER: Ok sure.

ASSISTANT: Sorry to say, no reservation found under your name.

USER: That's ok, thank you.

ASSISTANT: Most welcome.