I used to have a 4S. I had problems with it and decided to switch to s4 and I love it. One problem - my itunes. The guy in the sprint store told me about doubletwist app. It worked perfect. My phone could play the itunes songs and all was fine and dandy. However, I have a LOT of songs. I decided to get an SD card and transfer the songs onto there so I could free up some phone memory. When I transfer the songs from itunes onto my sd card they won't play. Probably due to the format of the itunes songs. What should I do?