You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I aid you today?

USER: I am Gregory Allen. Due to my scheduled exams has been postponed, I would like to change my existing reservation. Can you please help me with reservation?

ASSISTANT: Sure, we are glad to help you. Can you please wait for a moment, I will check with your reservation.

USER: Ok.

ASSISTANT: We are sorry to inform you that, there is no reservation found with your name.

USER: Ok, no issue. Thank you for your service.

ASSISTANT: Thank you for reaching us. Have a nice day.