******** Act- Deductions and Debt Colection

I cancelled my contract more than a year ago. I am now called by Shapiro Shaik debt collectors for a contract that is not active. Cell C have confirmed the SIM card is on prepaid, yet they also try and debit my bank account every opportunity they get. I’ve logged online queries and have called them to resolve the issue to no avail. Cell C has no claim against my name. This ******** act is creating a bad credit record for me. My recent reference for my query is ***, which they claim to be addressed yet I still get calls from these debt collectors.