False adivertis*****t on warranty

I bought a Willard battery 652 at Midas Pretoria North on the 26th of March 2020 and it had a 2 years warranty.The battery died before the 2 years and I took it back with my receipt but they keep on telling me stories that my alternater is the one that has a problem and I took the car for diagnosis only to find that the alternator is perfectly fine.i really don't understand their reason to decline my claim.How can I get help in this case?