You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I'm Donna Roberts.

ASSISTANT: Hello Donna.

USER: I would like to change my existing reservation due an personal issue, so could you please change my existing reservation?

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: Sorry Donna, there is existing reservation on your name.

USER: That's ok.

ASSISTANT: Would you like make a new booking?

USER: No thanks.

ASSISTANT: Ok, thank you for approaching us.

USER: Thank you.