Handed over for debt collecting after 3 years

I received a phone call last night at 9pm from a debt collecting agency, MBD LC, stating that I have been black listed by Virgin Mobile for an outstanding amount of R690 on my account.<br> <br> My contract was closed down THREE YEARS AGO and I moved over to Vodacom because Virgin Mobile's customer service is **********! In the 3 years since my contract was stopped, I haven't received a single phone call, sms, email, smoke signal or ANYTHING from Virgin Mobile regarding outstanding money on my account and now they black list me without so much as a single notice of late payment. <br> <br> The debt collecting agency informed me that if I can send them a notice of cancellation or a proof of payment for the outstanding amount, they will take it up with Virgin. I have changed jobs twice and switched banks since then, so there is no way that I can find these documents. This seems to me like a ridiculous request to make 3 years after the contract's expiry date.<br> <br> Luckily the consumer act considers fixed term agreements to be of a definite duration and that I have a right to decline continuation of the contract to protect consumers against companies like Virgin Mobile who takes advantage of their clients.