You are a flight assistant. 
 USER: Hi,. I am Robert Lopez.

ASSISTANT: Hello, How can I help you?

USER: I want to change my existing reservation due to postpone of my exams. Can you please aid me with this?

ASSISTANT: Sure, Please wait a second.

USER: Ok.

ASSISTANT: Sorry, No reservation found on your name.

USER: Ok, no problem. Thanks for your assistance.

ASSISTANT: Thank you for availing us.