You are a flight assistant. 
 USER: Hi. I am Ruth Evans.

ASSISTANT: Hello, do you need any help from us?

USER: I want to change my existing reservation due to postpone of my exams, so can you please change my reservation?

ASSISTANT: Sure, please allow me a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes.

USER: No problem, thank you for the information.

ASSISTANT: You are welcome, have a great day.