Bad Service!

My issue is that I signed up with Telkom for 10 gigs LTE at R249 per month, excluding calls. For the past 3-4 months, I have received invoices from Telkom for more that R1500. I sent you POPs for the amounts that I was told were outstanding. Where are all of these huge amounts coming from? I need an email for someone at the accounts department to explain to me exactly what these amounts are for. I am refusing to pay for Telkom's mistakes.