You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Myself Michael Williams.

ASSISTANT: Nice to meet you  Michael Williams.

USER: I want to change my existing reservation.Can you please help me out?

ASSISTANT: I am sorry  Michael Williams, there is no reservation found with your name to change.

USER: Ok, thank you for your help.

ASSISTANT: You are welcome.