there are probably 1000's of 4s users with a similar issue; are you still under warranty?
if so you should be able to get a replacement; if not then the official response appears to be "tough"
sorry I can't be more helpful, but thought I should tell you the position
there are many threads on the subject, you should read them and hopefully a suggested fix will work for you!
I believe this may be more along line of resolving your issue; it seems when you say the wifi won't turn on it may be greyed out due to a wifi antenna possibly being a hardware failure.