You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may 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, I am here to help you out. May I know your name please?

USER: I am Helen Green.

ASSISTANT:  Helen Green, we haven't found any reservation under your name in our database.

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

ASSISTANT: Thank you for reaching us.