Confusing and disappointed

I have been a client of Altech Netstar since August 2014.The company installed a 'Trekker' with early warning/panic button and permanent registration,in car.After installation,they fail to deduct the required monthly payment.I went to their branch several times,to report the matter and their employees always said that they will attend to the matter.Time passed (more than 18months) and then one day I saw a deduction from Altech Netstar on my bank-statement. I allowed the deduction to continue, but then, I also started to test the panic-button on several different occasions and situations,and their was no response from Altech Netstar:not even a phone call.Than a couple of months ago they send me SMS that the service is active. I than test the panic-button again,and once again,no response...As a result, I stop my payments... Now Altech Netstar ,is demanding payment for services rendered... They must please explain :WHAT SERVICE WAS RENDERED???