Consumer Redressal

i have purchased kent grand plus water purifier . on 29th jan. 2015 it stoped working and the service provider have changed all the parts of it, and charged me 3500 rupees . on 1st april 2015 it agin stopped working and the service provider asked me pay 900 rupees for again changing the parts which was internally fit. when i deny to pay him they refused to provide support and service. please help me on this. there was no authorised certificate of those parts which were previously fitted on to it. on quarry i found that they use to put duplicate product in the purifier and expect to work 1 month and again they charge for the same product. this has been a business for them .so please advice me that if we are purchasing an authorised product from authorised dealer is there no warranty on there parts?? when i asked them the the service provider said that there is only 3 days of warranty on electric parts. if after 3 days the electrical parts goes wrong we have to pay for it. help me.