Day time *******

I bought a new battery at Samsung,reason I bought it there so that it will laat longer,which it didn't,called them and advise of the matter they said I must bring it for assessment,when.my boyfriend came there as he was the one using the phone they deny battery they said it not theirs and it the one I bought from them,now the phone is not working because of the battery which will never be replaced. I'm very angry od their ********* behavior.