Faulty Goods without warranty

I bought a Willard battery for my vechile on 30.09.2014 at this shop they took out a closed unit and replaced it with an open unit and now the battery is faulty and I must pay for a new one because their old stock doesn't come with a 2 year warranty!!! It is unexpecteble they took advantage of a women whom trusted them and that what they were selling to her!!!