Settings>airplane mode must be OFF.
Shut off and turn back on phone (dont just put it to sleep, presspowr for 3-4 seconds until you see SLIDE TO POWER OFF)
Update your device's software.
Quick question though.. When you go to settings and wi-fi, is it on? if not, turn it on. Does it even give you the option to turn it on?
If its on, turn it off, then back on.
essentially what i am getting at by my last comments are, when the wi-fi Chip inide the phone goes bad, it will show wi-fi as OFF and will not even give you the option to turn it on.
save the restore as nw until after all troubleshooting as been done. Often times resetting the network settings will fix these things. SETTINGS>GENERAL>Reset>reset network settings.