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

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation, due to my last exams has been postponed. Can you help me with that?

ASSISTANT: Sure, I am happy to help you. Please be on hold.

USER: Sure.

ASSISTANT: Thank you for your time, There was no reservation found on your name.

USER: That's Ok, thanks for your information.

ASSISTANT: Thank you for choosing us.