Bad service received from them, demanding payments on service they didn't provide

They couldn't trace my car for the past two years,the offerd to sent. A technician until today, they never came but deducting money every month, I reversed the debit I,now they started calling non stop, but when I was supposed to be helped they were giving empty promises, I didn't renew the contract with them because they never give me a deserved service....what about the money I paid them past two years with the tracker that is not working... ****s