You are a flight assistant. 
 USER: Hello. Gregory Hall here.

ASSISTANT: Hello, what kind of help you are looking from our agency Gregory Hall?

USER: Due to sudden health issue, I am not able to travel in a flight on those date that I want to travel. So, I would like to change my reservation. Can you please help me out with that?

ASSISTANT: I am here to help you about that Gregory Hall.

USER: Thank you for considering my request.

ASSISTANT: Please be on hold while I will check in our booking list about your reservation to change it.

USER: Sure, take your time.

ASSISTANT: Sorry to say this Gregory Hall, there is no active reservation with your name in our booking list to change your reservation.

USER: Oh! I think the ticket was not booked due to server issue. Anyway, thank you for the information.

ASSISTANT: You are welcome, thank you for choosing our service.