Vodacom account disaster

I've just received a very rude call from HP Attorneys for an outstanding debt owed to Vodacom. I had a number of contracts with Vodacom and all of them have been moved to prepaid. The last one was moved about 6 months ago. I explained to the woman that called that I have confirmation that nothing is owed, and I have not received any invoices or statements since the beginning of the year.

She was shouting at me stating that I definitely owe Vodacom otherwise we would not be having this conversation.

Doesn't Vodacom read their own statements which read a 0 balance? If no invoices and statements have been issued for over 6 months why is there a debt collector calling me making wild accusations?

Please could you resolve this internal matter and not hassle me unnecessarily? I'm a business owner and do not have the time or energy for this...