You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I need to change my reservation as my plan to go for trekking got postponed. Can you help me?

ASSISTANT: Sure, may I know your name to check your reservation from our database?

USER: I am Ryan Campbell.

ASSISTANT: We regret to inform you that there is no reservation found on your name to change.

USER: Ok fine, thanks for your assistance.

ASSISTANT: Thank you for opting us.