You are a flight assistant. 
 USER: Hello. I am Jeffrey Campbell.

ASSISTANT: Hello, how may I render you?

USER: I want to change my existing reservation due to my health issue. Can you help me in changing reservation?

ASSISTANT: Sure, I will help you with changing your reservation.

USER: Thank you.

ASSISTANT: Please wait a minute, I will check and let you know the status of your existing reservation.

USER: Sure.

ASSISTANT: Thank you for your time, sorry to inform you that there is no reservation matches with given name.

USER: Ok, No issues. Thank you.

ASSISTANT: Thank you for reaching us.