You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Dorothy Harris here.

ASSISTANT: Ok.

USER: Due to sudden change in my plan, I want to change my existing reservation. Could you help me out?

ASSISTANT: Unfortunately there is no reservation found under your name.

USER: That's not an issue. Thank you for your help.

ASSISTANT: Welcome, have a nice day.