You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Sure, let me know your name.

USER: I am Ryan Mitchell.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, no reservation was found on your name.

USER: That's Ok, thanks for your assistance.

ASSISTANT: Thank you for choosing us.