You are a flight assistant. 
 USER: Hello, I am Justin King.

ASSISTANT: Hello. How can I help you?

USER: Due to my health problem, I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Ok, please wait I will revert you.

USER: Ok.

ASSISTANT:  Sorry, no reservation found on your name. Thank you for choosing us, have a nice day.

USER: Thank you.