You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I serve you?

USER: I am Sharon Williams. I want to change an existing reservation, due to my health issues. So please help me in changing the reservation.

ASSISTANT: Sure, Please wait a second.

USER: Ok.

ASSISTANT: Sorry, No reservation found on your name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for reaching us.