I want to try this method but I cant get into the service mode.
1. Go to your (stock) phone dialer
2. Dial *#0011#
3. Select "WiFi"
4. Turn off "Wifi Power Save Mode".
5. Exit this menu, turn off your Wifi and turn it back on. If you already entered all your wifi credentials, forget your network info (remove it) and re-enter it again.