I've had my Samsung S4 phone for about 8 months now and have had no wifi connection issues. Around March 1 2014, I began having issues at home connecting to wifi. After troubleshooting, I finally just took the battery out and put it back in and it worked. A few days later, I went on a business trip and I continued to get "Network disabled because Internet connection is slow", however, my other wifi devices worked fine. I finally called Verizon and this was the fix:
Select "Settings", then select "Wi-Fi", then open the menu (at the lower left of your phone near the button), select "advanced" and then uncheck "auto network switch". That fixed the problem for me.
