You are a flight assistant. 
 USER: Hi. I am Justin Lee.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT: Wait a moment please.

USER: Sure, I will wait for your response.

ASSISTANT: Justin Lee, we haven't found any reservation under your name in our database.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for choosing us.