Charged for false diagnostics

I took my Ford Fiesta into this dealership to have it looked at as it had broken down. The repairs department examined it and promptly told me that I needed a new alrernator as it was shot. They wanted to charge me over R6000 for the alternator and wanted me to order the parts and book it in. Because this didn't tie up with the burning smell we took it for a second opinion, turns out the alternator wasn't even the problem, the cylinder's had warped and the head gasket had blown because radiator hoses were broken. They charged us over R700 for the diagnosis and when asked they first accused my fianc?e of breaking the car, then merely apologized. We want our money back or an explanation as to why we paid when the main problems were not picked up. I nearly paid R6000 for nothing. My car would not have been fixed! Very very poor show from Ford!