Faulty cellphone

I bought a samsung galaxy j1 at jet in century city on the 7/9/2015.<br> For the 2days im using the phone now it freezes and gives a black screen. I need to remove the battery to get it going again for a while before it does it again.<br> <br> I figured seeing the device is only 2days old i will take it back so they can swap it out.<br> I explained to the sales lady whats wrong,she played around with the phone for less than 5minutes only to tell me theres nothing wrong with the device and theres nothing they can do.<br> <br> Shouldnt they have a 7day return policy?<br> I will never ever buy anything from jet ever again!<br> <br>