Bad credit score after receiving a wrong product

I was lead to believe that I was taking out a device and Mtn sim from Mondo. I was also told that they wil start to deduct the installment once the simcard was activated. On delivery I only received a simcard with no device. That was in September 2022. As of that day I never activated or used the simcard but they started deducting a R99 each month from dormant account. I was scanmed into taking their product that was not properly explained. This situation have a enormously bad reflection on my credit score/history. I am fed up and need this matter resolved and the negative listibg removed from ny credit report ASAP. Because I cant pay for a product I never used. I dont even have the simcard. I tried callibg various times but no one seems so help me. Next stop is the ombudsmen