You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I am Joshua Brown. I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, let me check the status and revert you.

USER: Thank you. Ok.

ASSISTANT: We could not find any reservation by the name you provided.

USER: No issue. Thank you.

ASSISTANT: Thank you for choosing us.