You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you at this moment?

USER: Can you please change my existing reservation?

ASSISTANT: Sure, we are here to help you to change it.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: My name is Mark Lopez.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Thanks for your time, there was no reservation found on your name to change it.

USER: No problem, thank you.

ASSISTANT: Thank you for availing us.