Failing to take responsibility for not fixing my car properly

I took my car to be reprogrammed at Lazarus Mazda Motors in Centurion with a new computer box after the old one was crashed during accident. The quoted me for reprogramming and while they were busy with it at the workshop after several weeks they realise that the wires are not okay and they gave me a call to fix them with an additional fee which I agreed to pay. They (Jakes) then called me to come fetch the car and they started it for me and all was well but the problem started when I tried starting the car at home it complained about not knowing my key's, I then took my car back for them to check what is wrong and then they tell me after couple of weeks that my wire were ate by rats and I have to buy a knew harness which I see as a story because I was even given this after calling them several times asking for feedback. I cant be paying R32 000 for the wires that they saying it was ate by rats at their workshop.