Useless service

I bought a new battery at the Battery centre Port Elizabeth. Within a month the battery had carbon thing coming out.i went back there,was told its just the terminal is dirty. Got new terminal from them they put it in. I've been having problems with that battery ever since and I kept going back to them.last week I went there yhe guy said the battery is fine just loose terminal. Today the car couldn't start and I went there.to be told there's nothing they can do now the battery is out of warranty.