You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I guide you?

USER: I want to change my existing reservation which is done recently due to some health issues, can you please help me in this?

ASSISTANT: Sure, please hold on for a moment, let me check.

USER: Ok, I will wait.

ASSISTANT: I am sorry, there are no reservations with your name. May I know your name?

USER: Sure, my name is Kevin Williams.

ASSISTANT: Thank you, have a good day.

USER: Ok, that's fine. Thank you for your service.