You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: My name is Nicholas Miller. I want to do some changes in my existing reservation, can you help me for booking?

ASSISTANT: Sure, please wait for a moment to check.

USER: Sure, take your time.

ASSISTANT: Sorry, no reservation found on your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us, have a nice day.

USER: Welcome. Thank you for choosing us.