I had two iPhone 4s, NOT two iPhone 4S'. (and updated to 6.1.3) One was stolen and then I was given a 4S. It had been reset so I had to restore my info to it That's when I noticed Wifi grayed out. I asked the previous owner and Wifi worked for them, however, they didn't upgrade to 6.1.3. I did and it doesn't work. It is a 6.1.3 issue and i hope that iOS 7 will fix it.