To resolve the heating issue please follow the troubleshooting steps provided in the given link: http://www.samsung.com/in/support/skp/faq/1119803.
Further follow the mentioned steps to resolve the network issue-
1) Reset Network Settings via setting>>general management>>reset>>reset network setting.
2) Ensure that network frequency of your device should be selected on Auto-mode.
Menu>Settings> Connections>More Networks> Mobile Networks> Network Mode> Select Auto mode (GSM/WCDMA/LTE).
3) You may check by exchanging the SIM in SIM slots.
For other mentioned issues, register your concern in Samsung members app(click on “+“icon>send feedback>Error report/ Ask Questions)
Team Samsung Members