Cell C billing canceled account

I canceled my contract with cell c a couple years ago. I do not use any of their services but I still had my old phone with the Sim card that I sometimes use as a back up. I keep receiving billing ranging from R5 up to R95. Luckily I changed my banking and none of the money was deducted but what if this affects my credit score!? I tried to search online if people had the same issues and came across an article where the company was in cahoots with third party subscription people who would send an sms and bill you for services you did not know about and ask for. I checked the bills received and they went back all the way to 2021 around the time I canceled my account. I've email customer service and I'm hoping to have a good outcome. I just think people should be made aware of this and make sure they are not being billed as well.