Worst possible service

Mtn is the worst thing that has EVER happened to me. I was with them from 3017 to 2019. I called in to cancel my contract. The debit orders would stop for a while and would continue. I was never issued some sort of acknowledgemeny of end of contract. I would continue calling. Up until I them decided to stop and reverse. Now I was handed over to the lawyers. For my sake I had to pay the ammount nu Debt management was requesting and now I'm struggling with a paid up letter. Nu Debt is saying they cannot provide me with the letter. I tried contacting mtn but I am failing. Now my credit score has been affected. I'm devastated!!!