You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I aid you?

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

ASSISTANT: Sure, may I know your name?

USER: I am Donald White.

ASSISTANT: Please give me a moment to check your ticket status.

USER: Sure.

ASSISTANT: Sorry Donald White, no reservation is available by your name.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for choosing us.