Bad service from Car Track

Cartrack has been mistreating me, i installed a car tracker unit in my NP200 as advised by my insurance at the time and we agreed i will pay R150.00 a month for the serives they offered, however, they were deducting R170.00, upon questioning this amount and trying to get back to the agreed amount, i was told the sales person did not give me the correct amount. I then said I can't afford the R170.00 hence i agreed to the R150.00 as it was within my budget. m I then decided to sell my car as it was a high-risk car, prior to the sale i tried calling them to find out what happen when i sell the car, for days my calls were getting cut off during the discussion and they would never get back to me. I eventually wrote an email to them which they further ignored until i finally stopped paying for the service. I then received a text and a call stating that my account is in arrears, that's when i explained to them that i tried to communicate with them, and I asked to speak to the accounts manager who to this day has never called me. Last year around November they called me stating they have handed over my account or collections, i explained the whole issues to the guy who called me and he never got back to me. I was then called by another lady asking me to pay the account in full, due to financial constraints i explained to them i can't pay more than R100.00 which we agreed on until i finish paying the account. Today i receive d a call from a rude lady saying i am paying a little amount i need to pay the account in full as it was canceled, he then told me they were going to blacklist me, i asked to speak to her manager, she just muted the phone and i was on hold for roughly 5 to 7 minutes assuming she is connecting the call to the manager, but that didn't happen. Their accounts team is rude and not helpful. The company was wrong in the first place, and they did not try to assist me in resolving the matter, instead, i am now told the R100.00 agreement is an arrangement made for 3 months or 6 months, but I explained that the lady who spoke to me never said there was a cut off period.