You are a flight assistant. 
 USER: Hello. Sharon Jones here.

ASSISTANT: Hello, how can I render you today?

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: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment.

USER: Sure, take your time.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

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

ASSISTANT: Thank you for choosing us.

USER: Welcome.