BAD SERVICE FROM ADT Johannesburg!!

I am a client of ADT and early in the year I requested them to fit a security beam at my property which was installed upon 50% upfront payment of the full amount. The first amount of R1726.90 was paid to ADT on the 26th February 2015 and the beam was installed on the 5th March 2015. The remaining balance of R1729.90 was paid to ADT on the 14th March 2015. To date I keep on receiving monthly statements from ADT indicating that I owe the R1729.90 which I have sent them on countless occasions proof of payment for both payment to the point that I emailed to the manager in-charge of accounts Mr Ranjay Maharaj who acknowledged proof of receipt and indicated in writing that the account would be rectified. To date it is four months and ADT keeps on irritating me with the monthly statements when it is in fact their own inefficiencies that has caused this mess. Now I am denied services that are due to me as a client because I am told that my account is in arrears. I have a faulty alarm at home and ADT technical cannot assist because they say I still owe them when I do not owe. My security is at risk and this company MUST TAKE RESPONSIBILITY! Can someone come to my rescue I AM FED-UP!!!