You are a flight assistant. 
 USER: Hello,. I am Nicholas Allen.

ASSISTANT: Hello, how may I aid you today?

USER: I want to change my existing reservation due to my exams got postponed.

ASSISTANT: Sure, could you please hold a moment, let me check your reservation and revert to you.

USER: Ok.

ASSISTANT: Thanks for your valuable time, sorry, unfortunately no reservation found in our database with provided name.

USER: Ok, thanks for your information.

ASSISTANT: Thanks for connecting with us, have a great day ahead.