Adt Security
Lack of service

I had a security system installed by ADT last year! after an attempted burglary into the property that I rent in Johannesburg. I paid the amount due in two installments, as agreed to. The second payment was made at the end of March 2013, by EFT, and to date if have not been able to get ADT to accredit this payment, despite me faxing and mailing proof of payment, in the form of official bank statements, to the company on various occasions. I have dealt with three people there to date and the issue remains unresolved. Phone calls to the official ADT line remain unanswered for up to twenty minutes and messages left, when one does get through, do not get returned. Then, in December, ADT took the amount that i paid by EFT in March, by stop order off my account, claiming it as still unpaid. What can I further do to resolve this issue?!