Mobile Mart, Gajuwaka - Cell is not working properly

I purchased the Celkon mobile from mobile mart at Gajuwaka, opp sBI Bank. After I bought my phone it is giving me trouble in incoming voice and battery backup. I went to shop on **/**/****. At the time of purchase, he told phone has a one-year replacement warranty. Today he is telling replacement warranty is applicable up to one week only from **th onwards he is postponing to next day. At last today he is telling replacement is not possible and he has not done the repair at least. He is taking irrespectively with us. Kindly take the necessary action.