Dstv debt collection

I have canceled my Dstv service in OCTOBER 2018. December 2018 I get a call from a debt collector attorney of Dstv notifying me I have bad debt with them. But the account is clear as per the call center system. After 3 calls and I have to proof that the account is cleared. But no email or reference number get given

Why do I get treated like a bad debtor but Dstv cannot even read and use their own system. Or notify the attorneys that the account is paid up