You are a flight assistant. 
 USER: Hi, I am Karen Parker.

ASSISTANT: Hello, How can I help you?

USER: I need to change an existing reservation due to postpone of my document verification in office. Can you help me in change an existing reservation?

ASSISTANT: Sure, Please wait a second.

USER: Sure.

ASSISTANT: Sorry, No reservation found on your name.

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

ASSISTANT: Thank you for opting us.