You are a flight assistant. 
 USER: Hello, I am Jeffrey Perez.

ASSISTANT: Hello, how may I assist you?

USER: My exams has been preponed. I want to change my existing reservation. Can you please help me with it?

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: Thanks for your time. There was no reservation found on your name.

USER: Not a problem. Thank you.

ASSISTANT: Thank you for choosing us. Have a good day.