Over billing people

I have been with cartrack since 2018,each month they debit different amounts and keeps calling me saying my account is in arrears even though I've paid. Today I received a xa3that my account is overdue by over R2000, 8 asked how cause last month it was I was told R.1.8k and paid and I was told they had not included October, November and December 2019, I asked how is that possible, been asking for a detailed statement for months. I'm being billed for things that are not active on my app and I was told there's over R80 for notifying them if I'm stuck. This is the worst company I've had to deal with