You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I assist you?

USER: I am Karen Perez. I need to change my existing reservation due to postpone of my exams. Could you please help me in changing?

ASSISTANT: Sure, please wait. I will check in the reservation list and get back to you.

USER: Sure.

ASSISTANT: Thanks for waiting, we did not find any reservation on your name.

USER: No problem, thank you for your information.

ASSISTANT: Thanks for approaching us.