unhappy customer

I have a unit in my car I have phoned them on many occasions that my tracker is not working nothing has been done or captured on there system yesterday 10.09.19 I phoned again asking what is happing the lady said there is no record of my calls I was shocked today 11.09.19 I phoned again well well my call of yesterday was not logged again my last placed picked up was 01.01.2019 I want my instalment back I I can not see why I must pay for a service I don't get I told that to the operator on the other side as well he said if I can proof it they can well I went onto my portfolio and there it is last updated 01.01.2019 what do I do