Bad service and old battery's

I bought a bakkie from BB Nissan Gezina. In less than 3 weeks the battery is dead. I received no assistance from them. They said that the car passed the batery test. After the investigation was done by Battery Center they said the battery was faulty and has already expired. I was supposed to get a new battery or compensated if you pay half a million rand for a car. What a **** BB Nissan Gezina has become. I don't recommend this dealership to anyone! Such a reputable conpany with such shady dealings.