Try Dialing *#06#, do you get your IMEI? Also, look in settings and see if your IMEI is listed there and also Modem Version. there are a few IC chips on the logic board that can lose connection, have bad traces (Pads) or just be in need of replacing.
Knowing if *#06# brings up IMEI and if IMEI and Modem are listed in settings can help know if you are experiencing a chip problem, software issue or just a antenna issue.
The Charging port has your "Data" antenna and your upper antenna is for your Wifi/Bluetooth/GPS