Never ending payment

Nedbank home loan - we sold our house at a defect of R170 000.00. Nedbank handed us over to Symington and De Kok Attorneys. These attorneys have been receiving payments from me on and off for 14 years. I eventually stopped paying as the balance is not decreasing. Nedbank should write off this debt as it is 15 years old. And remove my name from credit bureau as I have tried to offer an amount to settle but no feedback from Symington and De Kok Attorneys.