I purchased a white Tech21 Evo Check Case for my Samsung Galaxy S6 in a T-Mobile store a couple of months ago. The whole thing is now completely grey on the outside and is making my phone look dirty. The inside band is still bright white though. How can I clean my case and why did that happen to it? This case costs too much money to only last a couple of months. I love the slim, protective case, but I would like for my white cell phone to still look white inside the case. Do you have any other alternatives for a clear, protective case?