TK Attorneys harassment

TK attorneys are harassing me for a alleged amount of money owing to Ekhuruleni municipality in which I owned a property. I sold the property 5 years ago and have not lived there since. To sell the property, you require a clearance certificate from the municipality stating there are no funds owed or in arrears. I have this certificate clearing stating I owe nothing and yet TK Attorneys are stating I owe an amount of R40 000 for which they want to institute legal action.