You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Sarah Williams here.

ASSISTANT: How can I assist you today?

USER: Due to sudden health issue, I am not able to travel in a flight on those dates, can you please help me out with changing of my reservation?

ASSISTANT: Sure, I will help you on that.

USER: Thank you.

ASSISTANT: Please give me a moment.

USER: Sure, take your time.

ASSISTANT: Thank you for waiting, there is no reservation found under your name.

USER: Oh! I think the ticket was not booked properly while I am booking. Anyway, thank you for the information.

ASSISTANT: Welcome, have a great day.