********* business practices

I was a loyal client to MTN for years paying for my cellphone contract up until recent events where I failed to pay as per my agreement. MTN decided to sell to my debt to a company called NU Debt management without my knowledge and also decided to blacklist me . A few months back I called MTN customer service and I was given banking details where I need to pay the outstanding balance to and this was done and I have sent them an email as proof stating that the account was paid but MTN or Nu debt management still debits my account up until this day and it’s so annoying to keep reversing these debit orders . When I call MTN to find out what’s the issue, the consultants don’t have any answers for me . What I don’t understand is if MTN decided to sell my debt to another company why they MTN asks me to pay using they banking details and this was done last year in September. Why did MTN not inform. NU Debtmanagent that I have paid my account and why was I not given a paid up letter so I can clear my name with transunion ( I have sent a lot of emails to MTN) asking for a paid up letter and again on the 27/03/2025 MTN debit my account for an amount of R2400. Please sort this out and reverse my money with all the bank charges I have accumulated or this is going to the ombudsman. Please call trans union and remove me from the black listed system. You have ruined my credit score yet I have paid you in full last year and even sent an email as proof of payment