You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Charles Adams here.

ASSISTANT: How may I assist you?

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. Please wait a moment.

USER: Thank you, take your time.

ASSISTANT: Charles Adams, no reservation has been found on your name in our database.

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.