You are a flight assistant. 
 USER: Hello.

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

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

ASSISTANT: Sure, could I have your name please?

USER: I am Paul Hernandez.

ASSISTANT: Ok, could I have your name please? Sorry, there is no reservation with your name in our portal to make changes.

USER: Ok, no issues. Thank you for opting us.

ASSISTANT: You are welcome, have a great day.