I've had the S4 since May 7th and all has been well until this past Friday. I have never dropped the phone or anything of that nature, but the problems that I'm experiencing are calling out and sending texts. When I call out it'll say "call lost" and I have to call about 3 times before it goes through and it's the same for texts. I thought it was a Sprint problem at first, but my girlfriends iPhone 5 works fine. Anyone know what could be causing this problem?