You are a flight assistant. 
 USER: Hello.

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

USER: I want to change my existing reservation due to sudden postpone of my exams dates. Can you help me with that?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Could I have your name please?

USER: Sure, I am Janet Lopez.

ASSISTANT: Ok, please allow me a moment.

USER: Sure.

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

USER: Ok, no issues. Thank you.

ASSISTANT: You are welcome, have a great day.