You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: I have done reservation last night to have a trip but due to my sudden health issue I would like to change my reservation.

ASSISTANT: I can help you with that. May I know your name please?

USER: Myself Ryan Parker.

ASSISTANT: Sorry Ryan, there is no reservation found on your name. Thank you for choosing us.

USER: Ok, thank you for the information.

ASSISTANT: Most welcome.