Sold car with damaged battery and wont replace

So I went to right cars 3 weeks ago to buy a car, when doing the test drive, the car had a bad battery and had to be jump started at the gas station. So when purchasing the car, they gave me assurances that they had put in a new battery. So the battery they put in was a smaller battery for the car and a ****** with half a brain would have seen that because it didn't fit, but they still ended up selling the car to me like that, I went back to them to let them know they batery they put in is wrong and it's all messed up now and all they could say it's not their problem. Like cmon, I've dealt with ****tier service before but this place is absolutely the worse