You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Gregory Evans here.

ASSISTANT: How may I help you out?

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

ASSISTANT: Sure, I will help you in changing the reservation.

USER: Thank you.

ASSISTANT: Sorry, there are no reservations found.

USER: Oh! I think the ticket was not booked due to server issue.

ASSISTANT: Thank you for choosing us.

USER: Anyway, thank you.