You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: As my visa interview dates has been changed, so I would like change my existing reservation. Can you help me with it?

ASSISTANT: Sure,  I will be happy to support you. May I know your name for further proceeding?

USER: I am Mark Thomas.

ASSISTANT: Please give me a moment, let me check your reservation and back to you.

USER: Sure.

ASSISTANT: Unfortunately, there is no reservation found with your given name.

USER: No problem, thank you for your assistance.

ASSISTANT: Thank you for approaching us.