IPhone 4s wi-fi is not working .

IPhone 4s free sim. Not working wi-fi. First there were occasional breaks. Then more often. Now very rarely get to connect to wi-fi, once there is a break. In different networks. Started on firmware 5.1.1. On firmware 6.0, nothing has changed. At the factory settings, nothing has changed, too. Sometimes switch wi-fi is not available, a pale color. Similar problems with bluetooth. What to do? How to fix it? 😠