You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: Actually, I want to change my existing reservation which is done recently due to some problems, can you please help me in this?

ASSISTANT: Can I know your name?

USER: Sure, my name is Raymond Lewis.

ASSISTANT: Sorry, no reservation found by your name.

USER: Ok, no problem.

ASSISTANT: Thank you.