vodacom dont care attitude concerning my account

i had a contract with vodacom that expired last year and it was automatically put to month to month since i did not renew it.then i use it for 2or 3 month then i call vodacom to let them know i am not continuing with them they must make my number prepaid.following month they deducted money then next month deduction again and i didnt get airtime and data so i bought my own airtime and data of which was fair since i know i use and pay so to my understanding that was last payment with them. next month again they deduct some money from my account then i went to bank and reverse it.now i have been send to debt collectors and i am being threatened i called vodacom collection to find out whats going on.the rude lady told me all i have to do is pay that money to avoid being blacklisted and my number being blocked.so far they didnt convince me what am i paying for i even asked for statement they refused.i am so frastrated.i tried using their app to get access to my statements also they have blocked me.i think my rights as customer are being violated here