To resolve the issue please follow the below mentioned steps:
> 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).
> Search for the Network Manually by the steps as mentioned:
Menu> Settings> Connections>More Networks> Mobile Networks> Network Operators> Select Manual Search.
> You may check by exchanging the SIM in SIM slots.
> Insert different SIM card in your mobile and check if the issue is resolved or not.
If issue still exists, kindly visit the authorized Samsung service center with device and have it inspected for further resolution.
For address details of Samsung Service centers follow the link mentioned below-
Team Samsung Members