Mtn Promos

In May last year I received a call from Mondo/MTN selling me a 20GB contract for R100 only per month. I only received 3GB of data and the rest of their products were useless to me. They claimed it was because it was towards the end of the month and they calculate data and costs on a pro rata basis. I waited until end of June but I got the same useless contract and they opened another in my name each of which was R121. I did not use the sim cards since May as I was waiting for the correct contract. I was ignored for months but kept getting billed. I reversed all the payments until they responded to me. I continued to receive bills with a 0.00 balance, however the amount kept accumulating in the background when I checked my credit score. I was under the impression that they cancelled the contracts the entire time. Now I'm unable to get credit because I have defaulted on this account and I keep getting missed payments plus more debt from them. All this has been happening without any communication from mtn. This is total abuse from mtn as I cant even buy my first car as i am reflected as a bad payer. All my other accounts are in order.