You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Jonathan Walker.

ASSISTANT: How can I assist you?

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

ASSISTANT: Ok, please wait for a while I will check and let you know about your reservation.

USER: Sure, I will wait for your reply.

ASSISTANT: Sorry, no reservation found on your name to change.

USER: That's fine.

ASSISTANT: Thank you for reaching us. Have a nice day.

USER: Thank you for your service.