You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am George Allen.

ASSISTANT: How can I help 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 gleeful to help you to change your reservation. Please wait a moment.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for reaching us, have a nice day.