Bad service and company not keeping their promises

I bought a car battery(Duratec) at Midas battery centre at Gezina branch in Pta.I bought the battery on the 25/04/2021 and I was told that the battery has 24 months guarantee on it but I have to keep the receipt safe,I went to the battery centre today(30/05/2022) after I started to notice that the battery is starting to give some issues.The battery is not working as it doesnt have power anymore and im unable to start my car,I was sent back home after I was told that my car's alternator is faulty as the battery has changed its shape and i was told that the battery died because it was overcharged,Please assist as im not taking this explanation well and the only thing I need is to get a battery that is on a working condition.I asked if they can maybe include a clause or something when they sellthis products to us so we can make an informed decision.Please help