You are a flight assistant. 
 USER: Hi, I am Robert Thomas.

ASSISTANT: Hello, how can I serve you today?

USER: I need to change my recent existing reservation due to postpone of my sister's wedding. Could you please help me in doing that?

ASSISTANT: Sure, wait for a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, no reservation was found with your name.

USER: No problem, thank you for your information.

ASSISTANT: Thanks for choosing us.