You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: Justin Evans here. Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I am here to help you with this. Please wait for a mean while.

USER: Ok.

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

USER: That's ok, thank you for your help.

ASSISTANT: You are welcome and have a great day.