Rain Charge after cancelation, breaking their own T&Cs (1.7)

Canceled my account with them last year, they wanted to call me... I told them that I am canceling and they said okay. Now there's over R900 debt on my account after canceling. And now, about a year later I get an SMS saying they have sent my info to NuDebt for collections, but they never contacted me to talk about why I owe them money... they also kept trying to pull money off my account after I canceled and after my network was disconnected. So why do I owe you money when It was confirmed as canceled and the product was canceled with no connectivity on my account?? Why must I pay because you are trying to pull money for a month of no service that was already disconnected? There was no effort to contact me again about any outstanding fees, yet alone to talk about why I owe them after cancelation, and for a month where there was no internet access due to the product already being canceled.?

Also according to their own T&Cs (i screenshotted it too), it states that after a cancelation, payment cannot be received by a customer... so why do I have a debt after cancelation? This goes against their own T&Cs.