You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: My name is Mark Jones. I want to change my existing reservation, can you please help?

ASSISTANT: Sure, just a moment please.

USER: Sure.

ASSISTANT: I am sorry no reservation found on your name.

USER: No problem, thank you for checking it.

ASSISTANT: Thank you for choosing us.