Charged for false alarms due to faulty installation

I am a new Chubb customer and in October last year Chubb installed a new passive alarm sensor on my premises. The installation caused a plethora of false alarms due to faulty equipment supp**** and installed by Chubb. I cancelled my contract to end in December and my final bill (not delivered) included an extra charge of R114 which was taken by debit order. On enquiring I was told that it's for false alarms, despite having already discussed the false alarms in October and Chubb having agreed to waive this because of the faulty installation. I have never been bul**** like this before and it's theft to take my money for a job badly done by their own staff. If my money is not refunded I will become a major thorn in your side!