You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

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

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait for a moment, while I search for your reservation.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name in our system data.

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

ASSISTANT: Thank you for reaching us, we hope see you again.