None of these 'solutions' will work in the longer term. What is happening in most cases is that 2 pads under the baseband IC have become disconnected and need to be re-connected using micro-jumpers. This happens because the phone chassis is lightweight and flexes while in use and in your pocket etc, and puts stress on a joint under these 2 pins and eventually breaks them. Dropping the phone and sticking things against it might possibly help for a while (by pushing the pins against the underlying traces) but it'll always come back. The baseband IC is linked to the phone so you can't just replace it with a new one; you need to find a reputable micro-soldering technician who will remove the baseband IC, attach the 2 jumpers, reball the IC and re-fit it to the board. This is a difficult and fiddly job which is definitely not a DIY fix, but it will provide a proper, permanent solution rather than all this dropping your phone stuff.