MTN account handed over to nudebt

My account was handed over to indent. The collections company kept harassing me for my MTN account payment. I made the payment and they provided a settlement letter. Was promised my account will be cleared from my records. Fast forward 2 months later I contact MTN and they advise that I still owe them and no payment was made to them. Sent multiple emails but still nothing was done. MTN is not assisting and nudebt too. I’m beyond exhausted as this is affecting me. No one is assisting!!!!!!!!