I use a 3rd party voicemail system

recently One NZ enabled voicemail on my account (without notification) which intercepted all my forwarded calls.

I called them and had it disabled... (20 min of my life I wont get back) but the existing unheard mail is now showing up (like missed calls) on my iPhone screen.

Am I going to have to get them to reenable voicemail again to delete these?