You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am George Brown.

ASSISTANT: How can I aid you today?

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

ASSISTANT: Sure, I am here to help you with that.

USER: Thank you.

ASSISTANT: Just give a moment.

USER: Sure.

ASSISTANT: Sorry to inform this, no reservation is found on your name in our database.

USER: Not a problem, thank you for the information.

ASSISTANT: Thank you for reaching us.