Builders Hillcrest do not give refund for faulty lawn mower

I bought on the 13th of February a 4 stroke lawn mower make TrimTech at Builders in Hillcrest. It was a display item without packaging. The device was put into operation the first time on the 18th of February. It turned out, that the blade became loose also after several attempts to tighten it. On the 19th of February I brought the lawn mover back to the supplier and asked for a refund. That was rejected, but they offered me a quick repair on the same day. I got it indeed delivered in the afternoon. The following day, on the 20. of February we tried to use the lawnmower the second time. This time it did not switched on. After several vain tries I took the machine again and brought it back to Builders. Employees of the shop tried to switch it on too, without luck. I asked again for a refund and told the branch manager Mr Duncan Allan, that I will not accept a second repair on a brand new equipment . He is rejecting the refund ****her and was not willing, to give me the reason in writing. Builders have now my lawn mover and I lost R 4.320,00. I would like to know, for what is the CPA, if the consumer rights are ignored?