unauthorized debit orders

Can Vodacom kindly return my money for the OPPO that I finished paying in March 2024. My contract with Vodacom for my OPPO ended in March yet its June and they have added an ADDITIONAL R100+ on the debit. What the hell am I paying for when I'm done paying for the damn phone? They have my email address and cellphone number yet they have not bothered to contact me to notify me on why they are fooling around in my bank account. I don't work for you to do whatever the hell you want in my bank account. I have bills to pay