[Resolved]  Motorola, Moto Store Shop No 24, Charni Road Mumbai — selling defective pieces

i just bought a moto razr phone from this shop with a bill. the phone has started giving me trouble after only 2 days. i went back to them after 3-4 days but they refused to exchange the piece and kept it with them for 3 to 4 days saying it was under observation. they were very rude to me when i asked them to change it. dont know what to do. help!