You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I be a help for you?

USER: Melissa Mitchell here. Suddenly my friends changed the trip plan.So I want to change my reservation. Can you please help me for that?

ASSISTANT: Ok, please wait for a moment. Sorry, there is no previous reservation found on your name to change.

USER: Any way, thank you for the information.

ASSISTANT: You are welcome. Have a great day.