Theft

I have taken a contract with Telkom in April 2020,I have cancelled it 3days later cause I couldn't connect,the agents were so rude when I calll to ask for help,I decided to cancel it 3days later but every month they deduct money out of my account,I'm so frustrated cause I have to go to the bank every month to reverse and my main worry is now it is having a negative impact on my itchy,please help