You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Karen Perez.

ASSISTANT: How can I assist you at this moment?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure Karen Perez, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment to check your reservation status.

USER: Sure.

ASSISTANT: Sorry Karen Perez, no reservation has found under your name to change.

USER: Ok, no problem. Thank you for your information.

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