You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be at your service today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sure, I can change your reservation right now. Before that I need to know your good name please?

USER: Myself Brenda King.

ASSISTANT:  Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for choosing us.