Telkom taking my money for nothing

I am not able to cancel my contract in store and now after submitting forms to their online cancellation department in January I am still receiving invoices and debit orders are still going off. I am so fed up. They are a useless bunch. I have been paying for this service that I actually stopped using since June 2017. My contract period ended in August, but they say they just automatically keep it going if one doesn't cancel. I never signed for this. I don't know what to do to get these guys to just do their job and cancel my contract