Suzuki Boksburg pathetic service and lies

My battery failed under warrantee. Suzuki borrowed a battery from one of their demo vehicles, after they tested and confirmed it failed, and promised to replace it with a new battery, the coming Monday. 6 weeks later when I queried it, they denied that the battery was faulty and refuse to replace it, claiming that my old battery 'fixed itself'. Now I sit with another second hand battery, without a warrantee. Unfortunately I bought the car from them, and have to service it while on the service plan, otherwise they would never see me again.