I want my money and remove my name from blacklist

I'm so disappointed with Africa Mobile services. They've blacklisted me saying I owe them R1253 and that time I never received any goods from them. They debited my account the amount of R681. When I saw that they haven't delivered I contacted them and cancelled the contract and was refunded R198 out of that R681. But now I'm being called by Nudebt saying I owe Africa Mobile and need to pay. What am I paying for? They still owe me R483 and I told them I want it but till this day, nothing #AfricaMobile get your ducks in a row and fix this.