You are a flight assistant. 
 USER: Hello. I am Rachel Nelson.

ASSISTANT: Hello Rachel, how may I help you today?

USER: I am planning to change my existing reservation, due to health issue. Can you please change my ticket?

ASSISTANT: Sure, I will help you with this.

USER: Thank you.

ASSISTANT: Sorry Rachel, there is no reservation found as per your name to change your reservation.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for reaching us.