You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Christopher Turner here.

ASSISTANT: How can I help you?

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

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Please allow me a moment.

USER: Sure, take your time.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: Oh! I think the ticket was not booked properly at the time of my ticket booking. Anyway, thank you for the information.

ASSISTANT: Welcome, have a nice day. Thank you for choosing us.

USER: Welcome.