Telkom Mobile is *****ing from me

Telkom is taking me for a ride. They overcharged me last month by R202.70 on my contract bill. I tried finding out exactly what the charge was for as it just says Account subscriptions & once-off charges and the response I got back was that I had an unpaid debit order in January. I sent them 7 statements, went as far back as October 2019 and there has been no response. I even sent them my Transunion credit report showing that I've never defaulted on payments. Instead I got back an invoice of the amount that will be deducted at the end of April. My phone has never been disconnected, which shouldn't be the case if I had an outstanding payment