BAD SERVICE-FAULTY FRIDGE

I bought a Hisense fridge from Hi fi corporation in December 2013 and has three year warranty. The fridge started overfreezing and not cooling in the top. I reported the matter at the store,they assigned a technician on the 20/08/2015 and the problem was not resolved,I contacted Hi-Fi corporation again and they assigned a technician on the 26/08/2015. I contacted Hi fi corporation to infom them that the problem was not solved. The technician came again on the 28/08/2015 and told that he is going to replace sensors. The technician came again on the 03/09/2015 to repair the fridge and he tried to fix it but could not and told me that he cannot fix it and does not know the problem. I went to Hi fi corporation on the 03/09/2015 to inform them that the technician could not fix the fridge and does not know the problem. I spoke to Mamela who told me that she will contact the supplier to give her direction and will phone me the following day. I phoned their office on the 04/09/2015 and left the message and my contact details and there was no one who returned my call.