Am also facing the Network issue within this short Span of time. I have been using all the models in Samsung since its launch from the day. But when i tried to contact theChat support they say i dont have a sevice center near my zip code and he chat executive Bharath M said "In this case you need to send the device to service center so technician will physically diagnose the device and will identify the exact issue with the phone and will fix." which is ridiculous. He is asking me to get a loaner phone from the carrier but mine is an Unlocked 1 TB Version and Purchased directly from Samsung.com. He is also saying Samsung wont Provide Loaner Phone which is ridiculous. this is not the way they should treat the customers.
There's another thread where people are having issues on T Mobile and Sprint. My unlocked model has been fine on Tmo aside from slow data.
Mine started yesterday. My wifi of 866mbps that I usually use to game started giving me an error message that I'm not connected to a wifi when I'm trying to open the game. I thought It was my wifi so I reseted it multiple times and factory reseted it. Still the error message of I'm not connected to a wifi network poped up when I'm opening the game. I then went to school and connected on the fast school wifi and the error message still happened. Now I'm convinced that it's the phone and not the wifi network.
This year's realeses are so far the worst from Samsung. And they don't even care about customers since they won't read our posts and fix their problems.
Who is your mobile carrier? Have you ensured the device is fully up to date?
Have you tried resetting the wifi networks? Settings > Forget network? and Restarting your device and router?
We wanted to recommending giving this troubleshooting article a try: http://www.samsung.com/us/support/troubleshooting/TSG01001556/
Let us know if this resolves your concerns.