Old battery not given back to me so i need back

I bought a car battery on the 18th Septermber, and today on 24th october when I start the car, would not start, and the battery has a two years guarantee, I took the battery back, only to findout it has acid leaks all over.

So I took it back, they told me I must come back on thurdsday, which I refused, and I asked for a refund, they gave back my money after two hours fight, and I did not get my old battery they refused to give it back, please can you assist as I need that old battery back