You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my existing reservation due to my health issues, can you please help me with this?

ASSISTANT: Sure, can I know your good name please?

USER: I am Robert Lee.

ASSISTANT: Please wait a minute.

USER: Sure, make it fast.

ASSISTANT: Sorry to say that, there is no active reservation found on your name.

USER: Not a problem, thank you for checking.

ASSISTANT: Thank you for choosing us.