Usually I'm not a fan of phone cases that also have a built-in wallet. They're usually clunky, ugly and just use awful materials that ends up making you look cheap.
I have always been a fan of Mujjo, especially since they've sent out some of their products to me before to try out. I was very impressed by the quality and craftsmanship.
Recently they have launched a new line of cases - the low-key collection. They are beautiful, especially their slim fit iPhone leather sleeve and wallet. This gorgeous sleeve is made from one piece of real leather that is wrapped and formed into a fantastically classy looking sleeve. It also has a pocket for cash and cards, making it a perfect wallet too.