Prescribed debt

I’m getting calls from debt collectors saying they want to collect for FNB, I have been harassed of the debt not prescribed as per regulatory / law requirements ( South Africa is regulated by the Prescription Act 68 of 1969, together with the National Credit Act 34 of 2005). I have received multiple calls and sms form the debt collectors. When I call FNB they advised that they can’t see any profile on my account and I don’t owe them. I asked for the statement they advised that they don’t have any statement as they can’t find any profile on my Id number. Was also taken to the legal department they advised that there’s nothing on my name. I keep on receiving calls and sms threatening that they are going to put a judgement against my name I had loan with FNB many years ago, which the credit was about 28K. I have liaised with NCR regarding this issue and this account needs to be prescribed s per regulations. So am not sure who at FNB must do this prescribed debt removal. Can FNB remove the prescribed debt and send confirmation or send me a latter that I can send to the credit bureaus. Please attend to this matter soonest and mail a prescribed letter that this account is closed to ***.