I am sorry to hear that you're having issues with your voicemail. I have located your account from here and cannot find anything that explain your issue. I want to help your resolve this, so I am going to send you a private message.
I too have exactly this problem. I reported it via this forum some months ago but the engineer who called said it was not something that could be fixed from my end. I am tired of it now so I bought a standalone answering machine and want to turn the voicemail service off now please.