You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT:   Sure, I will help you. May I know your name please to check your reservation status?

USER: Myself Matthew Walker.

ASSISTANT: Walker, no reservation has been found on your name in our database.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for choosing us.