You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I assist you today?

USER: I am Dennis Collins. I want to change my existing reservation due to heavy rains. Can you help me with that?

ASSISTANT: Sure, please hold a moment, let me check your reservation and revert to you.

USER: Sure,.

ASSISTANT: Thanks for holding on, sorry, unfortunately no reservation found with provided name.

USER: Ok, no issue. Thank you for your service.

ASSISTANT: Thanks for your interest, have a great day ahead.