Please perform the following steps:
>Free some internal memory (If occupied more than 80%) (Settings > Device Care or Device Maintenance > Storage)
> Stop the background running app (Tap on the left soft key and close all the running apps).
>Check for the latest device O/S (Scroll down Notification panel >Settings >Software Update >Download updates manually).
1) Check Network mode and set it to Auto Connect. (Settings > Connections > Mobile Network > Network mode > Select LTE/3G/2G auto connect)
2) Search for the Network Manually by the steps as mentioned:
Settings > Connections > More Networks > Mobile Networks > Network Operators > Select Manual Search.
3) Check via another SIM card in the device.
4) Reset network settings (Settings > General Management > Reset > Reset network settings).
Note: Kindly once coordinate with the network service provider,
If still issue persists, kindly visit nearest service center for physical inspection of your device. Service center personnel will provide you the further resolution.
Follow the link mentioned below-
Team Samsung Members