I need to understand what's happening

I registered with unisa short course years back,they send me books and I wrote assignments, after a month of not receiving feedback, I phone them and I was told they don't see any records of me registering,I even explained that I have received booked but the lady disputed,after so many years now I'm receiving calls that I'm owing, last year I registered on line I received a confirmation that I need to resend my documents the once I send doesn't open,I did still no confirm, when I phone no answer