Well, in my experience, i have never stood for the purchase of faulty goods - no matter where they are bought from.
You have a right that, in exchange for your money, you receive an item which is in perfect working order.
If that item is faulty, then you take it back from a replacement or full refund - and if the replacement is the same, then go back again.
If the shop tries to fob you off with whatever, just explain that you bought a brand new phone, which turned out to be faulty and the replacement they gave you is exactly the same.
If they refuse to refund you, then tell them you will be willing to go to a small claims court to get it.
They dont usually like it when you threaten court action....