Cell C manufactured a duplicate billing for me!

I noticed in June That I was debited twice by Cell C for my fibre to the home service (I didn’t choose Cell C; my ISP was bought out). I’ve been trying to get it resolved using their useless, unresponsive email address and “Contact Us” website forms, but to no avail. I’ve just received my latest statement/invoice from them. Or should I say statementS/invoiceS!? Out of thin air, Cell C has created a duplicate account for me and started billing and debiting me twice each month. Here’s the thing, Cell C: my Account Number has been: * since you took it over. Kindly close Account Number: * and refund all amounts that have been debited to my account (May and June), and DO NOT debit me again for July.