Harassed by ADT's debt collector for false debt

I received a threatening letter of demand from Debt Source debt collectors saying legal action and blacklisting would be instituted against me within 10 days unless I paid an amount of R1896.39 directly into their bank account. <br> On phoning them I was told this was for an outstanding amount for an ADT monthly security contract which I had held from 2***. I challenged this saying that I had given notice on this contract and ended it legally and amicably at the time. ADT has never, either during or after the contract, made me aware of any outstanding amount. Suddenly five years later I find myself being threatened and harassed by a debt collector! I asked for information to be emailed to me from Debt Source so that I could investigate the issue. No information was forwarded to me in spite of me being given 10 days by them to pay the sum in their letter of demand. I also phoned ADT and am still waiting for them to furnish details of the issue.<br> The whole episode seems very ***** to me and smacks of an ******* attempt by ADT and their debt collecting stooges Debt Source to scare people and strong arm money out of them for non-existent debts!!!