Fraud with Consumer

I Have purchased micromax canvas 2+ on 31-07-2013, and during warranty period its motherboard has got some problem and was taken for servicing for 1 month, when returned it might still have some problem left due too which its battery had got problem and on asking they told its normal problem.

And now when its warranty had expired now they are telling that its a motherboard problem and it will cost Rs 4000/- in all.

Please help me out