WIFI Button is greyed out and does not turn on

Try the suggestions in this link: http://support.apple.com/kb/TS1559

Be advised that you may have a hardware problem.

Got the same problem, dont know what to do! used all my contract data too so i cant access the internet at all from my phone

Restart your phone without a sim card. Wifi should be working again. Put your sim back without switching the phone off. Worked for me

Nope, this doesn't change anything.

Same here have used all data. have you fixed your yet?

thankyou that worked for me to phew!! cheers

your awesome.

Hardware issue call apple support