well for me i removed my sim card set the settings to wpa (not wpa2 the first one) connected to wifi and used it for a while then inserted the sim and network is good as new
note:
the wifi indicator will remain white after connection and the speed will be VERY slow (around 15 kbps maybe or my connection sucks) this is maybe a problem in the chinese firmware (on mine that is)

Edit:

1.change the settings in the router options not in the phone
2.delete the access point from the phone and reconnect to the network

report back if this works