Cartrack big **** company debiting the amount we didn't agree on my contract.

Cartrack big **** company I install a track on my car first thing that was wrong their car it written two months free but it not true okay cool I keep on paying every month almost a year paying R120 last month they told me that am owing R723 because they put 2 devices on my car and the invoice have glitches ,I went to their branch in Bosburg the lady by reception call the finance office I talk to them they told me that invoice have glitches,I told them it not my problem they said they have a lot of consumers they can't review our invoices as clients at first time and now they keep on debiting R794.25 without my permission,I did payment arrangement with them but still they keep on debiting on my account the money we didn't agree on.😭😭😭😭😭😭😭.