Demand of payments that I made

I was having a contract with Cell C and I requested it to be terminated after 24 months at cell c w keywest. After paying my contact there was a debit order for 2 following months which i disputed. I contacted cell c and was informed that I subscribed something so im owing. My account was handed over to SSDA and i made payments for 3 months it was fully paid. Im now still receiving sms from SSDA that im owing cell c and the money has accumulated interests. I contacted cell c and SSDA i even emailed proof of payment to both companies but so fair they demanding payment of R200 again. Please hello peter assist ms i tried calling and emailing proofs but nobody is taking me seriously.