You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I need to change my existing reservation due to my exams, can you help me in doing that?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Please provide me your name to change your reservation.

USER: I am Jennifer Clark.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

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

ASSISTANT: Welcome, have a nice day.