MTN is a ****

In 2*** I took a contract phone with MTN (contract for 2 years and it was a debit order),was consistent paid in full. Come last month of the contract December 2021,did what I had to do called in and canceled the contract. Fast forward to 2022 September, I started getting calls for a company called nudebt sayings I owe MTN money, my account is in errors. Went to an MTN outlet and I found out that the mtn person I spoke to didn't cancel my contract instead they changed it from debit order to hand pay hence I don't get any debit order for the past 9 months. They said even if it's their mistake I have to pay. So I contacted the ombudsman, they took my case and I'm march 2023 I received an email from MTN apologizing and they even send me a paid up letter also promising that my credit will be fixed with a month. Fast forward to 2025 from march, I started receiving call from tl nudebt against MTN money and it's accumulating for the same contract fone. I emailed them the paid up letter from MTN and they referred me to mtn. We'll apparently at MTN no one is trained or qualified to help me with this because they move me from department to department with no way forward whatsoever. I've being calling for months now and they are doing the samething. Went to an mtn outlet and some lady tried to help by calling one of their department who literally refused to help nor refer me to their legal department.