You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: Sure, I am happy to help you and can you please let me know your name for checking purpose?

USER: I am Jonathan Williams.

ASSISTANT: Please allow me a moment to check your previous booking.

USER: Sure.

ASSISTANT: Thank you for waiting, there is no reservation obtained on your name in our back end to change your flight ticket booking.

USER: No problem, thanks for checking.

ASSISTANT: You are most welcome. Have a nice day.