Pathetic *********** service from Fidelity-ADT

I have requested ADT to upgrade my alarm system. It was arranged that they deduct the extra money for my new alarm system over a 3 month period. Less than 60 days after the alarm installation I tried to buy a smart watch via FNB but was instantly declined. When I logged in to Transunion I saw that Fidelity-ADT made a *****-up with my account as it was showing that I was R4617 outstanding and that I was 150+ days in arrears with my payment. I tried to contact Fidelity-ADT and eventually begged them to rectify their mistake and to restore my credibility but they simply do not come back to me. I am now black listed because of something that happened at Fidelity-ADT. And worst of all, I have never missed a single installment/premium on any of my accounts, ever! Another thing, my alarm subscription at Fidelity-ADT is deducted with a debit order, so there is no chance in hell that I can be 150+ days in arrears! Please can someone assist me.