You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

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

ASSISTANT: Sure, I will help you with that. Please mention the name for checking the reservation.

USER: Sure. My name is Christopher Nelson.

ASSISTANT: Please give me a moment.

USER: Ok, take your time.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Welcome, have a great day.