After upgrading my iPhone 4S everything worked just fine for quite a while. One day though I've noticed that I'm not connected to WiFi. Wired I thought, so I've reset the device and the problem was gone.
Couple of days later I got the same problem but this time neither resetting the phone nor the network settings have fixed the problem.
After digging on the internet for a couple of minutes I've stumbled upon an unusual solution:
Heat up the iPhone with a hair dryer until you get a temperature warning pop up saying “iPhone needs to cool down before your can use it.” (Have a cloth ready, the iPhone will get really hot).
Once this message appears, pop your iPhone into the fridge for 10 minutes to allow it to cool down.
Once that’s done—Wi-Fi and Bluetooth should work again.
I think there is a risk that you can damage your device, but since I'm out of guarantee I thought I'd try it to save time resetting the phone (I couldn't find a single post saying that resetting would fix the problem), contacting Apple and last but not least $200 for a fixing the phone. I've thought if I break it, I'll have to pay the $200 anyway, so why not try it? I wouldn't have tried it, if I had guarantee though.
Happy iPhone drying!
Two days after installing the 7.0.6 iOS Security Update, WiFi has stopped working again. It looks like I have to fire up my hair dryer again!
The hair dryer did the trick again! $200 + $200 = $400 saved so far!