You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation as my joining date got postponed. Can you help me in changing?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Can I know your name for checking your previous reservation?

USER: Sure, Shirley Thompson is my name.

ASSISTANT: There is no reservation found under your name.

USER: Ok, not an issue. Thank you for checking.

ASSISTANT: Thank you for choosing us.