Brits Ford service

Recently i took my Ford bakkie to Brits Ford because the bakkie's head gasket needed to be replaced. Luckily there were no major damage to the engine but still they advised me to replace the whole engine. I've been around the block a few times so i told them just to replace the head gasket. They responded that there is not enough tollerance to skim the head and replace the gasket. My response was that i have never heard of that. So they replaced the gasket after i went through the quote with them item by item and scratched unnecesary items. The whole ordeal cost me R24000. So i paid and went to fetch the bakkie and after a day or two i realised the radio is not working at all. It was working perfectly before. So i went back and asked them what happened and one technician came out but could not find the problem. So i went to the manager and he said it is electronic stuff which they can not cover. They then gave me a quote of about R20000 to replace the radio and said they worked on the engine and not on the radio. So they will not fix it. In my opinion it is obviously their fault and that they need to fix or replace the radio.