Try cancelling Telkom account...it impossible

I have been trying to cancell my telkom accounts since November last year. When i contacted them i was told to cancell online. Which i did..... i have received mails asking if i would like to cancel all lines which i clearly told them i would. So today i get another invoice for over R4000 ... really how does one cancel this service and why do i end up loosing the deposit i paid and i did do all i was told to do? Talk about terrible service....