COC STILL outstanding after paying R1000

In December, we had a burst geyser - which was apparently under warranty. Duratherm sent out a subcontractor to replace the geyser which they did after stepping onto the ceiling and causing damage. We had to chase the guys to come and repair the ceiling. Now that's done. We were also instructed to pay R1 000 for a compliance certificate, which apparently we HAD to do - we did this and got the subcontractor to sign that he had received the cash and would deliver the COC. To date - NOTHING!!!! I have called the number for Duratherm, but it does not work. I think we have been ****med - steer clear! Duratherm, I want my COC or my R1000 refunded!!!!