Harassment from debt collector sent by MTN!!!!!!!!!!

I opened a banking account with Standard Bank in 2021 and shortly after that huge sums of money were being deducted from that account and I was informed by the bank that MTN was responsible. I went to MTN to try sort this out as I did not have an account with them. MTN confirmed that there was no contract in my name on their system and that it could be a matter of *****. I was told to send an affidavit to MTN's ***** department, saying that I had not taken any contract with them together with other particulars, which I did. Since that time, NuDebt Management has been badgering me about this, saying that they are collecting on behalf of MTN wanting me to send them affidavits. MTN ***** department never came back to me on the matter but I am still being continually being harrassed by a debt collector who supposedly got my personal information from MTN. Can MTN get back to me on this matter and sort it with their debt collectors once and for all!!!!!!!!