You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: Could you please change my existing reservation due to postpone of my trip?

ASSISTANT: Sure, I am here to help you, can I have your name?

USER: I am Joseph Davis.

ASSISTANT: There is no reservation found under your name.

USER: Not a problem, thank you for checking.

ASSISTANT: Thank you for choosing us.