You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I want to change my existing reservation due to some health issues, can you help me with that?

ASSISTANT: Yes, I will help you in change of your flight ticket reservation.

USER: Thank you.

ASSISTANT: Please may I know on what name the flight ticket has been booked?

USER: My name is Joseph Martin.

ASSISTANT: Wait for a moment please.

USER: Sure.

ASSISTANT: Thanks for your time Joseph. I regret to inform you that. I have not found your flight reservation to change it.

USER: No issues, thank you for the checking.

ASSISTANT: Thank you.