You are a flight assistant. 
 USER: Hello, I am Gregory Walker.

ASSISTANT: Hello, how may I assist you?

USER: I need to change my recent existing reservation due to postpone of my exams. Could you please help me in doing that?

ASSISTANT: Sure, I can help you with it. Let me check the reservation list and get back to you.

USER: Sure.

ASSISTANT: Thanks for being patient. There is no reservation found on your name.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for reaching us.