Wifi of my 4S iPhone has grayed out within 3 months of my purchase. Now I have got a replacement piece from Apple which unfortunately only worked for 1 day and its wifi got grayed out..Can u help me as I have tried all means of getting it back..

Wifi of my iphone 4s has grayed out within 3 months of my purchase..I have now got a replacement from Apple but unfortunately it worked for only 1 day and the wifi got grayed out again...I tried resetting all my settings but all in vain. How many times have i to replace my iphone..Has Apple not thought of solving the wifi issues from the core. I have heard many users are having this problem. Why hasn't Apple taken any step to improve and solve this issue. After buying such a high end product, this is what u get??? Most of the Apple users are now shifting to Samsung phones..I was a great fan of Apple and have been using all apple products but this has really disheartened me..Apple please wake up!!!