USB wifi dongle with iPhone 4s?
This is how you fix this particular problem


  A common problem in the iPhone 4S, sometimes the Wi-Fi button will be
  grayed out and unclickable. This problem seems to be related to
  thermal shock — the problem may be temporarily fixed by simply putting
  the phone in the refrigerator for 15 minutes, or under a lamp for 30
  minutes.
  
  If this is the case, then the necessary permanent solution is to
  reflow the Murata SW SS1830010 Wi-Fi chip on the logic board.


https://www.ifixit.com/Guide/How+to+Fix+iPhone+4S+Wi-Fi+Grayed+Out/22167

Make sure you take it to a professional repair shop. Not a kiosk in a mall that does simple screen swaps. Not every repair shop is going to want to attempt this repair and some may try to rip you off and say that they can do it when they really can't and just take your money. Good luck!