Battery Issues-Rustenburg Hi-Q

I bought a car battery (Mazda CX-5) 5 months ago from Hi-Q in Rustenburg. The battery is now swelling and have taken it back to Hi-Q Rustenburg but they refused to take it back stating that they do not have guarantee on a battery that is swelling. If the swelling because it is a smaller size that was supposed to be their problem because they are the ones who sold me that battery and as service providers they were supposed to advise on the correct battery size. The guy who was assisting me was even rude. I do not recommend Rustenburg Hi-Q to anyone because they are friendly when selling and very rude is what you bought from them is faulty.